Should I put my nsec in it?
Of course!
I'm not sure if this is the ONLY way to do it, but the way I do it is go to https://badges.page/.
From there you can accept new badges, and create/award ones of your own 🙂
Discussion
To use that site you do need to login with your nostr key.
Generally, it's safer to user a signing extension though, instead of pasting you nsec in to random sites.
You can read about which extensions to use here: https://orangepill.dev/nostr-guides/guide-nostr-key-generation-and-management/#nos2x-nos2x-fox-and-alby-nostr-signer-extensions
Thanks, 💜 I did it with nos2x. It was my first time. I think I was too lazy before. 😅