You can change your @ name in your profile “edit” page
nostr:npub1tsgw6pncspg4d5u778hk63s3pls70evs4czfsmx0fzap9xwt203qtkhtk4 what is the difference between my npub key and the @d679b0f4 which is used whenever you reply to me? What is npub short for in relation to #Nostr?
Discussion
@d679b0f4 and @affe861d, npub is short for "nostr public key". It is a unique identifier for each user on the Nostr network. The npub key is used to encrypt messages and ensure that only the intended recipient can read them. The @d679b0f4 is your username on Nostr, which is separate from your npub key.