you use a tiny bit, like a dot. Don't put too much into it or else when you screw it in, it will make a mess. Make sure you use a nyloc washer between the screw and the led star. Also You can also use Nanotuner pad.
Since you are using 24 LEDs, why not just use 2 meanwell D driver. You can either use Reefkeeper lite ALC to dim it or built a simple dimming circuit. Nanoreef has it. Also if you do not want to go that option, you may have to use light diffuser or hang it higher