If I use the up2date tool in redhat and lets say I type in
/usr/sbin/up2date glibc
And it downloads all the files to make glibc work, but does it actually install them for you, or do you have to install them after it downloads it?

do a up2date --help and that will tell you how to use up2date

usually up2date -u will download and install everything for you

The default action up2date takes after downloading a package depends on how you intially configured it. However, you can cause it to always attempt a package install by using -i in your up2date command.

Your best bet is still to do up2date --help and figure it all out yourself though...