Sry for making it too hard to understand... I really ran out of time to make a good in-game guide...
So the first thing to do in each round is to control your movement. You can decide how much energy to put into this turn's moving phase. The energy input will be converted to "movement output" according to your mecha's state (if your jetpack or legs is destroyed, you can only move a shorter distance with the same amount of energy input). Then you can choose to move either closer or further.
Then you have to decide which attack to use in the attack phase. You can choose multiple attacks in the same turn as long as you have enough energy and they are performed by different parts. You can also use arrows next to the skill button to decide how much "fate fuel" to put into this attack (or charge for CORE BEAM). After confirming, you then need to choose the target enemy body part for each attack.