how can i make documentation for my app ?

hello friends , i try to upload my first android application but isn’t ready to be published because of documentation .
and this is a part of the email that i receive from envato reviewer team :

"The documentation is a little lacking.
Most importantly, remember that buyers may not be technically inclined. They may just be looking for an item to drop into their existing code base. Also keep in mind that a typical user won’t really know about all the features your system brings to the table. With them in mind, you should also look into providing a quick start guide of some sort. It need not be long: a short one will do. "

any help , any advise , any documentation template ?