There are 2 types of finishes — enamel and catalytic (self-cleaning). The catalytic surface is specially treated, so it requires care when using (see manufacturer's instructions).
It is easier to clean the oven while it is still warm, but not hot.
Remove shelves and other moveable parts and wash in a hot-water detergent solution.
More stubborn spillage may require the use of a commercial cleaner (see manufacturer's instructions).
Wipe over oven shelves, occasionally rubbing with a soapy fine steel-wool pad.