roller skate wheels
Your wheels slot onto your truck axles and are held in by a nut.
Fasten the nut all the way in until it stops (without applying too much force or you might damage the bearings), then turn the nut back a quarter of a turn.
Your wheels should spin freely. If they make rattling or clicking sounds when spinning they might be too loose and should be tightened by adjusting the nut.
If you are a beginner, tighter nuts will make the wheel spin slower which can be good for learning. You can loosen them off as you get more comfortable to increase your speed.