A combat round consists of 2 turns. 

Action turn: A character can allot action points here to take an action.

    - Example: Knight uses 10 Action points to take 2 attacks with their sword.

Reaction turn: A character here can allot action points they havent used to take a reaction.

   - Example: Rogue uses 4 points to evade one of the attacks

In a combat round, everyone's turns are taken at the same time, and the Reaction and Action turn happens at the same time. The way this works, is players tell their gamemaster beforehand what they do during their Action turn. The gamemaster then announces every player and npc's Actions, and opens the Reaction turn, which is taken the same way. Every player tells the gamemaster beforehand what they wish to do. The gamemaster can then narratively explain how each action and reaction applies narratively, either before, or during rolling of the actions. When players tell the gamemaster what they wish to do, this can either be done publically in a more relaxed easy going game, or privately for a more tactical and realistic game. Personally I'd reccomend doing it privately, since this rewards cooperation and teamwork to a higher extent. 

When a player levels up, they get Abilities from 3 sources. 

Linear path - This is the path that grants a baseline for all players. If the setting your game takes place in contains a Linear Progression tree, each player gets the improvements linked to each level. These may be things like: Stat increases, skill points, hit point increases. and similar.

Skill trees - This is the path that uses points granted from a class or linear tree, to improve various aspects of your character. If your setting utilizes this form for progression, then skill points should be awarded from either base progression, or from in game sources if the skill trees are supposed to be magical enhancements from the world, or something similar. An example of this progression type may be a combat tree containing the ability to use certain weapons. 

Class progression - This form of progression is tied to classes, if your setting includes classes then this progression type should provide certain benefits tied to your class, and potentially subclass as well. For example a Knight could gain stat increases to strength, and a base deduction of 1 cost of AP to attacks and blocks. While a subclass to Knight, being Swordsman, may get Longsword knowledge, and a bonus to damage dealt with Longswords. A Class Progression path could be either linear, or using Skill tree and Class Points, or a combination. Alternatively a third way of doing class progression is a Linear tree that contains paths that be used to split or merge the path to allow minor differences in each instance of a class. For example a lvl 5 ability for a Knight could either be less AP reduction on Armour Weight, or more damage, and then the tree can continue at lvl 6 with either merging into only 1 option again, or continuing down with a split tree providing an offensive and a defensive version of a Knight tree. 

Any of these progressions could be in the setting, or could be excluded if the setting does not allow for it. And each type can have gaps that provide nothing if that is desired.