>>2574981spool tension knob, #5 on pic related, loosen it completely, then wobble your spool back and forth inside the baitcaster. Tighten the spool tension until the spool stops going side to side, it's now completely adjusted and shouldn't be touched. Every once and awhile check the side to side play hasn't come back.
All adjustments are done with your brakes. Turn all of them on or max settings, get used to throwing lures. Load up the rod and slowly let the rod do the work, don't force it. Have your thumb on the spool at all times until you get used to it, as you cast, let off the pressure on the spool with your thumb and let the spool let out line on the cast but still having minimal enough pressure for when it starts to backlash, you can slow down the spool.
When you get better, lower the brake settings.