Well, basically, you would:
Download the tarball (the zipped archive of source code)
Then from the BASH prompt:
depending on what zip method was used
tar xvf tarball
Unless you want to fiddle with compilation options, or the source code is unusual, those are the steps you'll generally want to take.
A read thru the LFS handbook can teach you a lot about compiling. So can creating an LFS system, of course, but it takes a while