MMmm.. as all previous posters have already stated.. it looks awesome for your first try.
And as all of the others have said you need to roughen the surface of the plastic up with some sand papper. Put a layer of spray primer, let dry and sand again. Put on another layer of primer, let dry.. and then! you are ready to start painting.
Warhammer has some great colors that can be used... but they are expensive and painting all the armor peices is, imo, not worth it. Try to find some spraypaint instead. Though you'll have to bring an adult. There is an age limit of 16 (or 18 i think) to buy spraypaint in sweden.. (Damn those vandalising little punks!)