I was given a macbook air and when i open it up it has a circle with a exclamation mark in the inside how do i go about restarting it back to normal

Follow the steps in the support document you posted from to boot into recovery to install macOS.

Alternatively see here: link-> About macOS Recovery on Intel-based Mac computers - Apple Support

If you see the globe and warning symbol, try these solutions:

• Make sure that your Mac can connect to the internet. If you're not prompted to choose a Wi-Fi network during startup, choose a network from the Wi-Fi menu , if available.
• Press Command-R at startup to try using the built-in Recovery system instead of internet Recovery.
• Connect to the internet using Ethernet instead of Wi-Fi, or vice versa.
• Connect to the internet from a different Wi-Fi or Ethernet network. Your network configuration might not allow the internet access that macOS Recovery needs.
• Try again later, because the issue might be temporary.
• Start up from another disk or volume, if available, or use a bootable installer to reinstall macOS.

If you still need help, please contact Apple Support.