i need assistance re-setting my MacBook Air to factory settings in prep for trade in

You follow all of the steps here:

https://support.apple.com/en-us/HT201065

Main points: make sure you sign the device out of your Apple ID/iCloud account and make sure you have a full backup of everything on an external drive.

I need to erase my McBook Air for a trade.

Have you tried to click on the link provided in the post right above yours? it contains all the instructions.

restore MacBook Air to factory settings

Read above instructions from Apple.