Briefing
Base64 turns binary into printable text. It is trivially reversible:
base64 -d encoded.txt Objective Decode encoded.txt to reveal the flag.
Stuck?
Take it one step at a time. Ask for a hint here, or type help in the terminal to
see the commands this challenge is about. Typing hint works there too.
That is every hint. If you are still stuck, run help in the terminal.