Nick welcome.
Is it RIB (rigid hull) or SIB (soft bottom) you have?
You need:
STEERING
1. A steering wheel.
2. A steering cable (for a boat that size I assume you are not looking at hydraulic but simple teleflex type steering)
3. The helm unit (the bit that links wheel to cable).
4. A link bar which connects the other end of the steering cable to the engine (and the necessary bolt, washer etc).
The helm unit will come with instructions. Getting the cable length right is important, you don't want it turning too tightly.
ENGINE CONTROLS
1. Throttle box
2. 2x Morse cables to link throttle and gears (again need to be the right length)
3. Possibly a conversion kit to attach the engine end of the cables depending on the engine model.
4. Wiring loom - at the very least you will want the kill cord at the throttle end, but choke, start, stop, etc are all common to control from the key.
ELECTRIC START (OPTIONAL)
Before long you will start to think getting up to pull the cord is a waste of effort.
You'll want a battery, battery cables, isolator switch, battery box and an electric start conversion (which may be the most expensive bit of the whole thing!) as well as potentially needing to upgrade any electrical output to be regulated. Beware its a slippery slope - next you'll be wishing you had power trim... If you are buying an engine for console steer consider buying with all these bits ready rather than upgrading but I'm guessing you are in the <30HP range so may find them much rarer second hand.
CONSOLE
Which may or may not include a jockey seat
You need to mount this very solidly - they take a huge twisting force under tight turns. How you do this will depend on your deck.
My tip would be to do as much of the additions to this (cutting holes, fitting gauges, steering etc) before fitting to the boat. Its a lot easier to do on the bench than when you need to crawl on the deck of the boat and half inside the console to tighten a bolt.
If you buy a bare jockey console (probably most suited a to a boat your size) you'll need a cushion and upholstery, will probably want a back rest too.
If you are actually looking at a SIB with a removable seat then things will be different and you'll want to keep it all simple to make it quick to rig.
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