I see this is your first post, so I'll 'try' to be gentle...
I don't know which brand you have, but it doesn't really matter for this purpose. You can go to Dometic's or Thetford's website (the two most common brands), for example, and you might find a manual. But, this is as about as dirt simple as simple gets.
-- Fill the top section with water
-- Pump a little water into bowl
-- Do your thing
-- Pull handle to flush (well, 'drop')
-- Add a little deodorant chemical if you want
-- Use only RV TP
-- Disconnect top from bottom to take bottom section to a land toilet to empty
-- Should I remind you to first lift the lid... or can you figure that part out? Hey, I did 'try'...