The best way for a prior Windows user to think of the way Ubuntu and other Linux distributions install software as something like the Apple App Store, or the Windows 8/10 store. In most Linux distributions the place to get software (store) is in a repository, and one system can have many repositories. What a repository looks like to you is a website with some special qualifiers at the end of it.
There are two main ways to process the install of whatever software, through the GUI and via the command line.
This Wikihow site shows both in a basic overview
The GUI way you go to Dash or other software discovery app (it varies by Linux flavor) find the software and click install/open, simple.
The difference from Windows is that since whenever Linux has been around, the GUI is always based on command line commands, so that is why you get recommendations to use it instead. It is a bit of a learning curve but the benefit is that at some point managing Ubuntu will become very easy.
Normally there will be some software that you will be able to find that is already available to be installed such as Adobe Flash (or open source alternatives). Below would be how to install the Adobe flash version.
sudo apt update
sudo apt install adobe-flashplugin
Seen above the sudo command precedes the package installer apt with it's own command update which tells apt to go off and pull the list of the latest versions of everything, so that when you tell it to install the package adobe-flashplugin it gets the most current version. If you issue the commands above and you get something like "[yourusername] is not part of the sudoers file..." you can try this askubuntu post to set it up.
A word of caution, Adobe Flash will one of these years cease to be updated and therefore should be considered unsafe to run on any operating system. The web is littered with the talk of it for years.
To find what to install normally a quick web search such as "Install Filezilla Ubuntu 16.04" should yield some sort of step by step result or package. If it doesn't you can try searching for the package in the default Ubuntu repositories by using a GUI package manager tool different from Dash that lists packages in a searchable chart format. The one that is mostly recommended is Synaptic. Run this command:
sudo apt install synaptic
It is fairly straight forward to use, you can search for package and then sort by name, read the details, and then click install. Be very careful with this tool though, as if you remove packages, you can mess up your system in a hurry.
When you cannot find whatever package you are looking for and the driver disk like your label maker says "compile this by.." then before you go start trying to compile drivers you should try to search for precomplied binaries for your Ubuntu version.
For example my Samsung printer has a repository that has precompiled drivers for all the printers that Samsung makes. When you google say "Brother Label Maker ubuntu repository" or "Brother Label Maker Ubuntu PPA" (PPA is a label for a repository) you may find specific instructions on how to add it. You should make sure that the repository is maintained by a reputable official looking source before you add it. BUT generally they are, and for 16.04 there are two methods to add it.
If it gives you a PPA you can add it by issuing commands like
sudo add-apt-repository ppa:[repositoryname]
sudo apt update
If for example it does not mention a PPA but gives you something that looks like an internet address you can do something like this. I will use virtualbox as an example.
On their install website they say add the following line to the sources.list file:
deb https://download.virtualbox.org/virtualbox/debian <mydist> contrib
Where <mydist> refers to the codename of your version, for 16.04 it is xenial. To find this run the following command:
So after that you should have:
deb https://download.virtualbox.org/virtualbox/debian xenial contrib
Now to add the repository to the sources.list file run the command:
sudo nano /etc/apt/sources.list
Use the arrow keys or PG DN keys to go to the bottom of the file, and add the line in. Press CTRL + X to exit and say Y to save the file.
Next, you need to get the key for the newly added repository, so that Ubuntu knows that the added repository is signed and a valid source. There are many methods to do this, but basically they will ask you to add a text file with the key to your system. Either you download the text file, or you issue commands to combine the downloading with the command to add the key file. If you download the key file run the command:
sudo apt-key add keyfilename.asc
Or combine the downloading of the keyfile with downloading
wget -q https://www.website.com/download/keyfilename.asc -O- | sudo apt-key add -
Once the key is added run:
sudo apt update
FYI there is a new version of Ubuntu 18.04 and it may already have drivers for some of your hardware built in as the kernel is newer. As a FYI brand new hardware sometimes takes a while to have full support on Ubuntu as kernel versions are fixed and branched to the release.
If you are then left with compiling a driver from source you should specifically search for an example of how to first set your system to compile drivers, and then find an example that matches your situation.