I have looked allover but I must have missed how to edit my name. I think I used my Google account to sign into area 51Buddhism if that helps.
I started with an unregistered account called Samadhi, couldn't log in and I register another account with the same name Samadhi. It is possible to merge the two account into one seeing that I've accumulated some points in my first account.
Your profile is displayed at https://buddhism.meta.stackexchange.com/users/151/user535875 (for meta) and/or at https://buddhism.stackexchange.com/users/151/user535875 (on the main site).
The two should be linked, editing one should edit the other; but you cannot edit your meta profile, therefore edit your profile on the main site.
On the 2nd line of the (main site) profile page, to the right of your name, immediately under the line which says "Questions" and "Tags" and "Users", there are links which say "edit" and "privileges" and "preferences".
That "edit" link is what you want to click.
That will probably take you to this URL which will let you edit your profile: https://buddhism.stackexchange.com/users/edit/151