Sorry if you think that there is a lot of mystery with compiling from source, cause from my experience it isn't really too bad. To compile there are three main steps: tar, make and make install. There are some other steps that you can do between the make and make install steps but those are optional. So let me start at the top.
cd to /the/directory/that/has/your/file in your case it would be Desktop.
tar -xvf 1.3.12beta.tar.gz
sudo make install you need to be root to install a program
Those are the simple steps for how to compile a program.