I am brand new to Linux, having just got going with Yellow Dog 3.0.1 (as I use a PowerPC machine). I have downoaded File-roller, Firefox and several, other install packages.

I seem to manage to extract them but still can figure out how to actually get them to install so they are operational programs. As I am so new to Linux, I still really stuck using the GUI as my means of navigating or instructing the computer. I don even know how to log in as root! Can anyone talk me thorough installing software in simple plain english steps, that assume absolutely no prior knowledge? Your help would be much appreciated!

just untar the package , u could use ark or in the konsole type :
cd <the folder that contains the package>
tar -xvzf packagesname

then for installing it type :
./configure
make
su
<your password>
make install

also its better to read the readme file and the install file that comes in the tar file