how do i restore my macbook air to factory conditions

Hi Myrna

You can use MacOS Recover (restart holding Command and the R key) ⌘·R and from there, you can use disk utility to erase the install volume and then reinstall the MacOS. This is okay if you're not planning to give away or sell the Mac.

If you want to completely wipe everything, then you can use Internet Recovery to install the MacOS that came with your computer (restart holding Shift-Option-Command-R) Shift·⌥·⌘·R. You will have to wait for the recovery software to download from the Internet. How to reinstall macOS from macOS Recovery - Apple Support

If you've decided to sell or give away the Mac, there are some steps you should take beforehand. What to do before you sell, give away, or trade in your Mac - Apple Support

See: What to do before you sell, give away, or trade in your Mac - Apple Support

Reboot it and hold “Command and R”. Then, you will see something saying OS X/macOS Utilities. You are in recovery mode.

Go to the top amd you will see Utilities, click on Disk Utility, and click on your disc name, then click Erase.

Now exit disk utility and go back to Install macOS/OS X.

Click on reinstall “macOS/ OS X”. Click your erased hard drive and reinstall the OS.

Good luck, Christian