Quite honestly, it is easier to clean and maintain a crate located indoors as opposed to one located outdoors. When it is outdoors, it is most likely to have insects living in it. It is also exposed to harsh weather conditions. The summary is that you will have to clean an outdoor crate more often.
Generally, you will need mild soapy water to clean the crate; you can use a soft brush for a more thorough cleaning. Make sure you rinse it out properly when you are done cleaning. If you have some accessories like blankets, pillows, and pads inside the crate, be sure to clean them out or wash them appropriately from time to time. Wash the fabrics in a washing machine and dry them properly.