How to change icloud account on iPad?

Be aware that if you sign-out of iCloud and other Apple services - and allow another user to sign-in - you’ll not be able to change back for 90-days. This restriction, intended to prevent account abuse, cannot be bypassed.

To sign-out from iCloud:

Settings > [Your Name / AppleID] > Sign Out

Once signed-out, you can sign-in with a different AppleID.

If your intention is to fully reset and use the iPad with an entirely different AppleID, as a different user, you would be best advised to follow this process to properly prepare the iPad for reuse:

What to do before you sell, give away, or trade in your iPhone, iPad, or iPod touch - Apple Support

This procedure will sign-out from all services, completely erase the iPad and remove the Activation Lock.