MacBook Air says "storage is full", how do I clean up?

Hi vibha67,

Welcome to the Apple Community where some of us do our best to help each other.

Apple Support have an article online to help you:

How to free up storage space on your Mac

https://support.apple.com/en-us/HT206996

I understand files stored on the desktop take up more memory /storage space than the same files put into a "Desktop" folder.

Sometimes there is a lot of storage space used up by the Trash Bin. You might want to check and/or empty it.  

(You likely won't see the amount of storage differ until you "Restart" your computer.)

Best place for accurate info. on storage / space:

See used and available storage space on your Mac

https://support.apple.com/en-gb/guide/system-information/syspf9b375b9/11.0/mac/11.0

Hope this helps :)

Transfer files between two Mac computers using target disk mode

If you are lucky - you may be able to transfer enough files off this computer to allow it to boot up. Then follow pervious instructions to make additional Empty Space. To guard against this - one needs to keep 10 - 15 GB of Empty Space available at all times for the computer to function properly

Trying to download Big Sur. Not enough space on my MacBook Air