Help, re-setting service indicator

[Rich 525i]

Hi, this is my first post so sorry if its not very clear.

I've had my 93 525i sport for a few months. It needed a stage II service so I had it done at the local garage but I need to re-set the onboard computer, it still comes up with the orange and red service light when I turn it on.

It also sometimes comes up with tail light, number plate light, brake pads randomly but they are all working fine.

Can you tell me how to do it? I have heard it is relitively easy.

Rich