How to use excell

As Excel, part of Microsoft Office, is not an Apple product, I strongly recommend asking in the Microsoft Office:Mac forums here:

Office for Mac

Everyone there is a Mac user AND an Office user, something you can't say about Apple's forums. You will get the fastest help there and I think you will find the contributors more than helpful.

However, if you are just starting starting with Excel, I strongly recommend finding someplace in your area that offers classes in Excel, because nether the Apple or Microsoft forums are suitable venues for "start-from-scratch" tutorials.

You can look up a manual on it or a YouTube video