You'll need to tie the deck fitting into some primary structure. Different approaches you can take. Some people add a small bulkhead and fabricate a piece to connect the deck fitting to the bulkhead. Other people will use a piece of wire rope
and tie into primary structure. I suggest hiring an appropriate professional to come over and consult with you. You also need to consider how the loads to the mast
are being handled. Some boats will require running backstays
to be added. Then once you sort out the stay, you'll need to figure out how that sail is going to be sheeted.