Sliding the crumb tray out on a Delonghi toaster oven makes dumping out most of the mess easy. To clean the oven more thoroughly, wait until it has cooled, and clean the interior surfaces (but not the coils) with a damp rag dipped in warm, soapy water.
Before you clean your Delonghi toaster oven, make sure to unplug it from the wall. The baking and broiling trays have nonstick surfaces, and they both slide out and clean easily in the sink. The oven also features two flat racks, which you wipe clean with a damp, soapy rag and then follow with a rag damp with just water. Do not use anything more abrasive on the interior of the oven, as that can damage the nonstick coating.
With other attachments, such as the rotisserie spit tool, clean it using the same process after you remove it. Make sure that everything you take out of the toaster oven and clean is completely dry before you put it back in the oven, as moisture and electricity do not mix well at all. For questions about how to remove specific attachments and items from your toaster oven, consult the relevant section of the owner's manual.