So yeah in Coinos you need to "sign" the action so that Coinos knows you are authorizing the creation of this NWC key. The simplest way to do this is to jus t pase nor nSec or Nostr secret key. This is not the most secure however.

Using Nostr connect, or what I use Alby is a safer method, kind of like having a hardware wallet that signs Bitcoin transactions offline for you.

For now I would just use your secret key but maybe explore the other options at some point.

Do NOT use it on the one you just sent the screenshots of however, delete that one and create a whole new NWC in Coinow. You want to keep that QR code / key safe, don't show it to anyone.