Start with the
JO7110.65AA and associated notices. The pdf is 794 pages.
Then you have to memorize the airspace over which you will have control. All navaids, airway radials, procedures, etc.
Then you have the applicable letters of agreement, coordination protocols specific to your airspace, etc.
Then you need experience in evaluating the traffic situation, formulating a plan, and implementing it. That takes a lot of practice.
It takes several years from hire to reaching full qualification at your facility. Washout rates are high.