How to edit excel file on iPad?

Download MS Excel for iOS from the App Store. All MS office apps are free for iOS. On an non-Pro iOS device, you will need to create a free Microsoft ID and sign in to actually edit and save documents. If you have an iPad Pro, you will need a paid MS Office 365 subscription to use the apps.

See https://support.office.com/en-us/article/when-do-i-need-an-office-365-subscription-b6518311-893a-4a89-bfcd-bdc56bf52085

If you already have a personal or business MS Office subscription for the Mac, then just use that same MS login on the iPad with the MS Office apps.