Name Change

CyberCannibal wrote:

... my MacBookAir given to me without master resetting

I interpret that to mean the previous owner of your Mac did not comply with the requirements in What to do before you sell, give away, or trade in your Mac. If that is the case, your Mac cannot be used in its present condition.

Your options are as follows: have the previous owner comply with those requirements, return it for a refund, or erase it completely and configure it as your own.

I will take the liberty of assuming the last option (erase and reconfigure) is the only one available to you, in which case you will need to skip all the way to Step 8 of those instructions.

Be advised that if the previous owner protected that Mac from unauthorized tampering (to prevent a potential thief from using it, for example) you may not succeed, and you will be stuck with an inoperable Mac. There is no recourse, so let's hope you don't arrive at that conclusion.

Whenever you acquire a pre-owned computer you should always perform a clean install of the OS by first erasing the whole physical drive before reinstalling the OS. Who knows what nasty surprises the previous owner may have left behind.

@John Galt is absolutely correct that you need to be extremely careful with pre-owned Macs since the Mac may have a firmware password lock enabled, or it may still be managed by the previous owner. Performing a clean install will also quickly alert you to a firmware lock, but if the Mac is still being managed, then you may get a notification during the initial setup after a clean install, but sometimes you may not get a notification until weeks or months later. If a Mac is still being managed or has a firmware lock enabled, then you will never be able to disable them so the Mac should be returned for your money back.