I am assuming you are referring to this file :
What you have to do to install this :
tar -xzf gyach-0.9.4.tar.gz
^this will unpack the archive
^ this will set up the stuff necessary to compile the program
if this does not complete successfully, post your results here and I'll let you know how to procede
^this will actually compile the program. again if it fails post your results here.
^ this must be done as root because it installs the program in areas that a regular user account is not allowed to write to
I must say that if you can find a RedHat RPM for this program (i did a quick look and didnt' find one) then that would be much easier.
if you have any problems with this, post your problems and we will try to help you get this done. Do you know there is a Yahoo Messenger for RedHat? Check yahoo's website to find it.