resolution:

how to find what is taking space?
use diskusage or storage usage, not sure how to find this from cmd prompt but most likely there is a way also.

how to free space from home location etc?
if un-installing has been done and the app is still taking space, then open cmd prompt, then sudo gainroot, then remove folder left behind: example to remove openarena left behinds: rm -r /home/opt/openarena

This could be fatal if you delete critical files/folders needed by the system

List of additional useful commands to be used via cmd prompt:

ls = list directory contents
cd = change directory
cd .. = one directory up
mv = move
cp = copy
mkdir = make a directory
rm = delete (-r foldername / removes folder)