usually tar.gz and tar.bz2 are source packages so after unpacking them, you have to ./configure && make install, but it's not always true.
To unpack tar.gz you can:
tar -zxvf cream-X.Y.tar.gz
To unpack tar.bz2 you can
tar -xjvf cream-X.Y.tar.bz2
for more info
then if there's a README, or INSTALL file, there should explain dependencies, or way to install the package.
If there's no unmet dependency,