you write a cheque and post it with your provision form i think and send it off where it tells you to send it off.
you can even pay for it by postal order which you get at the post office (i did this. its easy)
i think they charge you 2 quid for the postal order sevice which i think i had to pay.
if you read the form you get with it, it tells you what to do and ways you can pay and it even gives you an envelope with the address you send it to already on there.
i send off for one about 5 months ago and everything you need to know if on a little booklet you get with the form