When we had a Deere planter on the same principle, we would "list" the ground in the spring, that is, create beds and furrows, and we would irrigate down the furrows. Come planting time, you run the "buster sweep" (big plow in the front) down the middle of the beds.
The idea is to peel off weeds and dry dirt, and just plow deep enough to get the seed into good moisture. Then the little chisel in the middle scratches out a furrow for the seed, and the discs run at a little bit of a toed-out angle to throw dirt back on top of the seed.
Your discs on the side are geared to a mechanism to rotate the plate, the ring at the bottom of the hopper. Looks like your plate has about 8 holes in it to drop seed. As it rotates, the holes fill from the hopper, go under the little mechanism at 10 o'clock of picture three, and drop the seed down a tube.
The wing nut at the bottom will probably remove to allow you to remove and change the plates for different types of seed.
As far as adjustments, you'll need to either hold your depth with the tractor 3-point hitch, or add gauge wheels to hold a constant depth. Ideally, you'll run it pretty level, but you may have to run it a little nose low to get the busters to dig in. You can't run too far on the nose, or it will lift the row units out of the ground. The chisel in front of the seed tube might also be vertically adjustable.
The single spring on the front of each unit is to adjust down pressure. It also appears that the discs have adjustments so you can adjust the toe-in. The wing nut on the back of the hopper is to remove it to dump it out and clean it.
Next time, look for a John Deere 71 flex planter. Much more versatile, new enough (1960s) to still have parts.
