how to reset a macbook pro A1502 i bought to factory setting once you are locked out of it

What do you mean locked out of it?

Do you mean you forgot the macOS user account login password? If so, it can be reset using the information in this Apple article:

https://support.apple.com/HT202860

Do you mean the laptop has a message of "Disabled"?

Or do you mean there is a padlock on the screen which indicates a firmware lock?

Or do you only want to perform a clean install of macOS by erasing the internal drive and destroying all data on the internal drive?

How to reinstall macOS - Apple Support

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