Horus 361

Ive recently bought a YBR125 and im loving it, its my first bike and ive found it a joy to ride apart from the headlight (which Ive replaced) and the thin tyres (which im about to replace,) However I dont have a clue about bikes and although I check the oil occasionally its hasnt needed topping up yet, but when it needs topping up I have no idea which oil I shoud be using? Ive only done 500 or so miles on it and it was serviced just before I bought it, How often would you reccomend getting it serviced? many thanks Todd