I do not currently have a user password or an account on this MacBook

my uncle has given me his MacBook Air and it just came in the post. I opened it and it has opened at the user password setting. I do not currently have a user password or an account on this MacBook, but I was told that it was sent back to me in the condition of factory settings. There is no option to shut down or restart the laptop, the only option is to sign into an account that is not there? Can someone help me through this or do I possibly have to log in as my uncles old account? Very confused.

[Re-Titled by Moderator]