Defense is an under served part of chess study. Puzzles are almost always offensive focused, but if you go to Puzzles->Custom Puzzles, and select only Defense, you might find that helpful.
But for specific advice, never make a move before looking for moves and tactics that your opponent might have, even in moves that seem purely positional or like a standard recapture.
In the following article there are several videos cited that relate specifically to defensive issues. They can be located by searching for any of these words - 'defend', 'blunder', 'lose', 'mistake'...
Improving Your Chess - Resources for Beginners and Beyond.....
https://www.chess.com/blog/RussBell/improving-your-chess-resources-for-beginners-and-beyond
The following instructive book by Dan Heisman deals specifically with defensive technique in chess...
Looking for Trouble: Recognizing and Meeting Threats in Chess (3rd Ed.)
here is a peek inside the book...(Kindle version; 3rd Ed.)...
https://www.google.com/books/edition/_/i1ngEAAAQBAJ?hl=en&gbpv=1
As a complete chess novice, new to chess.com I've started to look at the principles of opening and played my first game or so as white. Recently I was given black and realised I had no ideas on what to do.
How do I get my first steps learning the basics of defence from the resources on chess.com?
Thank you.