Ubuntu is not like the Windows operating system you are used to. Old habits are hard to break but the sooner the better. You're gonna have to scrap the whole mentality of downloading an .exe from whoever and installing whatever to your system. That's one of the many reasons windows has so much malware (although, Netbeans Java and Virtualbox etc are better off downloading from oracle IMO).
One of the advantages of running a linux operating system is that most programs ("packages") are installed through a package manager. This is similar to the "app-store" or "google-apps" and even more like "homebrew" if you are familiar with OSX.
You don't need to download the source of the source package to install a package (program) using Ubuntu. All you need to do is type
sudo apt-get followed by the package name. To install gcc-4.6 and build essential open a terminal and type the following commands:
sudo apt-get update
sudo apt-get install gcc-4.6 build-essential
If you see no errors, the package is installed. If you need to see if any gcc packages are installed, you can type the following command in an open terminal:
dpkg -l | grep gcc
The output will list every package installed containing the letters gcc in the name. No output = no packages installed.
Will list all installed packages.
To search for available packages related to "netbeans" you can type the following command:
apt search netbeans
To narrow the results, type this command instead:
apt search netbeans | grep netbeans
Another search example:
apt search c++ | grep compiler
Finally, you can install a GUI frontend (synaptic package manager) to help you search for and install packages by typing the following command:
sudo apt-get install synaptic
Search for synaptic package manager amongst your installed apps or open a terminal and type the following command: