[xs83]

You need to use it as your primary OS and learn by doing.

Start on the basis that you shouldnt have to download something to do what you need, it all comes pre-installed and go from there.

Need to process some text files? Use awk & sed etc Need to partition and format a drive? use fdisk, parted etc Need to encrypt a drive / folder - use LUKS

Everything you need is on the system itself including the files to run tests on, the rest of it will come with normal usage.