Mike on Nostr: There is an option to copy and paste you nsec (private key). Apologies, I don't know ...

There is an option to copy and paste you nsec (private key).

Apologies, I don't know what the exact terminoligy it will use, but something like "I already have an account" or "Paste in your Private Key"

If you're not sure where to find your nsec, look in the key management section of your existing client.

I wrote some articles about NOSTR here:
https://habla.news/u/mhardcastle@nostrplebs.com

I would start with this one here for some basic concepts:
https://habla.news/u/mhardcastle@nostrplebs.com/1725913455892