Succulent plants usually have really tiny dust-like seeds. In some cases, it's hard to imagine that a tiny seed like that can grow into a large healthy plant.
Because the seeds are so small, it takes special care to get them planted and growing.
Any time you have seeds too small to see without magnification, you need to worry about the slightest breeze blowing them away, or too much water in a forceful stream washing them out of the soil.
When I grow succulents from seed, I always use sterilized cactus and potting soil mixed together one part each, or Sunshine Mix #4 which has extra aggregate for drainage.
This ensures that the soil will hold a bit of moisture yet not get waterlogged. Any excess will drain away quickly.
For a large quantity of seeds, use a shallow flat filled about half full with the prepared soil mixture.
Lay a dowel on its side down the length of the flat and press into the soil about 1/8" so the seeds have somewhere to go if they get blown around or washed out of the soil.
Don't cover the seeds with soil, that's not necessary. Use a fine spray nozzle to water them, even after they germinate.
If you just have a few seeds, sprinkle them on top of the soil in a pot.
Choose the pot based on the ultimate size of the plant.
This will allow you to leave the young plants in the same pot for a while, and they'll still have room to grow. If the pot is too small, the seedlings will be straggly and weak, and fall over and get tangled.
Mulch with turkey grit or fine gravel (not sand which will clog the pores of the soil, preventing drainage). See more about looking after succulent seedlings.