apt-get is already a quite easy tool to install package, but I found some problems with it.
Hope the members of the fourm would help me to figure out what's going on

# apt-get install rar
warning: cannot get exclusive lock on /var/lib/rpm/Packages
Reading Package Lists... Done
Building Dependency Tree... Done
The following NEW packages will be installed:
rar
0 packages upgraded, 1 newly installed, 0 removed and 92 not upgraded.
E: Could not get lock /var/cache/apt/archives/lock - open (11 Resource temporarily unavailable)
E: Unable to lock the download directory


Whatever I apt-get install something, I got the above error, anyone can explain what's going on please? Thank you for the kindly help : )

it looks like you must have another instance of
apt/dpkg/dselect/aptitude/etc -- something running already
with a lock on the apt cache
you will need to stop whatever process has the lock to free apt for access