Beginners rigging question...
Small daysailor rarely have topping lifts. Instead you gently lower the halyard until the boom is either in a boom crutch or on the deck. The Main halyard is typically used to support the boom once the mainsail is down. If you do decide to rig a topping lift it could be run as suggected but it would normally run through a block at the end of the boom to a cleat on the side of the boom close to the mast. The cleat That you describe is probably for the outhaul.