You still didn't get an answer to this, because there is no single answer. A
.tar is just like a .zip, it might contain anything. Most often, it will
contain the source code for a program, which you need to compile. But there is
no single way to compile!

Perhaps the program is written in C, and requires X, Y and Z libraries to be
installed on your system before it will compile. Or it could be written in
BASIC, and need a completely different approach.

I have even seen a .tar which contained an executable program and some
instructions on how to run it, no compiling required!

So the general approach is, set up an empty folder and expand the .tar into it,
then look at what you've got. If you are lucky, there's a text file called
readme.txt which will tell you what to do, in something approaching plain
English. I've also seen text files called descript.ion, usually written by
smartasses. (Present company excepted, of course.) I have even seen
instructions written into the program source code, as comments. In the worst
case, you just have to look around, viewing everything you can, and if that
fails, search the Ubuntu Forums with the program name.