There is a drain plug on the bottom of the case.Make sure you have a gasket on it when you reinstall it.The fill cap doesn,t have a stick but the case is marked for 900ml.Just pour a liter in and your good as long as you have no leaks.As far as oil you,ll get a variety of answers.Some use Auto trans oil for cars.Others run 10w30 or 10w40 but made for motorcycles/wet clutches.DO NOT USE regular motor oil.
Search the thread as far as what to use for Trans oil or look in the manual.Also depends on what temp your riding in.I used to run Automobile trans oil and change it often but have switched to 10w40 kawi oil as it protects better and I have a bunch laying around.