How to install app from source code?

[DTi4565459]

I can start gnome-session, then mount CDROM #4 from 6 disk set, and then find 
the .gz and .dsc files.  But that's as far as I can get.  Which debian 
install untility will work with these packages?  I could try to do it from 
command line if that would help.  If I click on a .tar.gz file the Olde M$h*t 
way in the Gnome File Manager, the source code will display as text, but no 
install program gets initiated.