To road register you need to get a registration number issued, then get plates made by approved supplier (i.e. garage - you will need to show them the official grant of registration number from DVLA), affix the reg. plates then tax the tractor - as agricultural machine. Tax discs are now discontinued so just keep hold of the confirmation of taxation you'll get from DVLA. MOT not needed, road use insurance is required.
Finally, just double check your driving licence and make sure you are licensed to drive a tractor! (I'm sure you have, but better safe than sorry!).