The prime qualification for admission into the Royal Arch is to be a Master Mason, of at least four weeks standing, in a Lodge under the United Grand Lodge of England, or a Lodge under a Grand Lodge recognised by it.
As in all other Masonic Orders, you will need a proposer and seconder who are members of the Chapter in which you seek to be exalted. Members of your Lodge who are Royal Arch Masons always wear the jewel of the Order with their Craft regalia and will be delighted to be approached about membership.
Often your Lodge will have a Royal Arch Chapter attached or an arrangement with a local Chapter. You may decide to join an attached Chapter or to widen your circle of friends by joining a Chapter in another Masonic centre.
If all that fails, contact the Provincial Secretary.