Prize gaming permit
Licensing authorities are responsible for issuing prize gaming permits. For a full explanation of what this means, read: Gambling Commission, prize gaming permits
You will need to apply to the licensing authority where the permit will be used. This is usually the local council, if you do not know who that is, see: Gov.UK, find your local council
To apply, you will need to download the correct form and send it back to the relevant licensing authority.
A full list of fees can be found in the related documents section.