How to reset the oilservice indicator lights????

I've got a very cool BMW E28. I just got it. When I bought it the Oilservice indicator lights where on. So I changed the oil in the engine and replaced the filters (oil and air). But the lights keep on burning. Now I found out you need some sort of device to reset your cars computer, but I don't have one (of course). Does any of you guys know how to reset the thing manualy? And does someone know how to check if the computer is still functioning properly? If any one can help I'd be pleased.

Danke!

Bertje.