step one: unpack the package to a directory...
#tar -xvvzf foopackage.tar.gz
now you should have a directory named after the '.tar.gz' file... well most of the time.
step two: enter the directory, and compile some code!
At this point you should be able to run the program where it stands, compiled within the directory.
If it works the way you want it.... move to step 3. If not, then play around with compile option or add any missing libs.
step three: install it system wide...
You can always see if there is a masked version in portage that you can install... Gentoo might have a 2.0 version that's masked (or hard masked for that matter).