When I downloaded a theme, .tar.gz or .gz or some kind of format like that. When I opened it, it was just a folder full of files. How do I make it a theme or something?
Some theme authors include an install script in the archive; if you find a file called INSTALL or something similar, extract the archive to a folder that is preferably easy to get to. Then open the terminal and cd to the applicable folder (probably
~/Downloads by default). Then in terminal, run
./[Name-of-Install-Script] to install.
You will need to open your archive manager as root. Use Alt+F2 and type
gksu [packagemanager] where [packagemanager] is the command for the archive manager. (In not too heavily changed Ubuntu installations, this is
file-roller.) Open the file, then extract the entire package to the directory
/usr/share/icons for cursor themes or icon themes).
Next, you will need a program to apply the theme. I suggest the GNOME Tweak Tool. Install this by opening the terminal and typing these commands, one by one:
sudo add-apt-repository ppa:ricotz/testing sudo apt-get update sudo apt-get install gnome-tweak-tool
Once this is done, you can either search for the tool in the HUD or run it directly by pressing Alt+F2 again and typing
gnome-tweak-tool. In the dialog that appears, there should be some options on the left for "Theme". Click that, and change the theme settings to your liking. The effect should be immediate.
The Community Wiki recommends that you extract the archives into either
~/usr/share/themes or icons to
The recommended application to manage themes,
unity-tweak-tool, is available from the Ubuntu Software Center.
sudo apt-get install unity-tweak-tool
Alternatively, you can visit the project page http://ubuntu-tweak.com/ and download the debian file package. Ubuntu-tweak offers more configuration options than just customizing unity themes.
I had previously copied the recommendation for the Myunity tool from the Community Pages, but it is no longer receiving popular attention. The only thing close to an explanation that I could find in the forums. Searching this site, it seems that MyUnity is 3rd party software and is the solution for Ubuntu 12.04, but that the unity-tweak-tool is preferred for newer releases (my inference).
Additional edits incorporate advice from this answer.