I have a garage on some land I have used this garage for

In essence to claim the land you will need to show that you have been in possession for at least the last 10 years. Possession here needs to be demonstrated by some intention to show ownership of the land such as tending to the land or fencing. You must demonstrate an intention to own, which again could be covered by the previous point. It must be without the owners consent which is self explanatory. You must make the application on form ADV1 accompanied by a statement of truth or statutory declaration which has a number of requirements so I would recommend you hire a land law solicitor to assist with this, the form can be found here: https://www.gov.uk/government/publications/adverse-possession-registration-adv1. You must list all the documents accompanying the application on form ADV1 and pay the appropriate fee under the Fee Order. If you do not complete the form correctly, the form ADV1 may be returned to you. The statements of truth or statutory declarations should be factual and, ideally, the person making the statement or declaration will use their own words rather than language copied from precedent books. The person should expressly state how the facts are known to them, if this is not implicit in the statement or declaration. Once completed the form and accompanying documents will need to be sent to HM Land Registry to inspect and make a determination.

Yes that would be enough but you still need to actually make the application to get it registered as above. I trust this assists