You need to fill in an AML-1. If you don't have any you should phone your local council's Trading Standards office and ask them to send you some. Or you can print some out, but it's easier to have the proper forms as they are coloured carbon copies.
Print from here:
http://gov.wales/topics/environmentcountryside/ahw/farmanimaltracing/animalmovementlicences/amlsheepandgoats/?lang=enIf you do print them you will need to fill in FOUR copies, one for the local authority, one for you, one for the transporter (you), and one for the abattoir.
Make sure your animal is properly tagged - ie double tagged with EID. Record the tag numbers on the movement form. You can phone your abattoir for their address and CPH number in advance so you can fill that in before you go. Explain that it is your first time and they will probably be very helpful.
Also withhold food the night before - i.e. bring him in (or pen him up) with just water. No grass or hay or hard feed. This will ensure that he has an empty belly in the morning which the abattoir will want for hygiene reasons.
Also you will need to tick the FCI box on the form - confirming that you have satisfied any withdrawal periods for any drugs that you might have administered.