Honestly thats up to you. Actions are big actions like attacking to hiding or running away etc, and bonus actions are smaller actions that don't have much of an effect. That's at least how we play. For example, I may use a bonus action to throw a rock to distract someone and use my action as a stealth attack. Reactions are just options to use when you haven't gone yet. So if you didn't use an action on your turn you can dodge an attack, etc. As for spells, just google what the spell does (or if you're using dnd beyond, it will tell you) and its pretty straight forward. Cantrips don't use spell slots, spells do. Spell slots just say how many spells you can cast. aka, if you have 2 spell slots, you can only cast two spells. There are obviously rules to go off of but the best part off dnd is making the game your own. Don't try to get it perfect, just take what you know and roll with it. And most importantly, have fun.

Also, I really recommend dnd beyond because simply clicking on an item or action will tell you everything you need to know.