how do you get energy?

[Comguitoz]

title

[darKatana]

If you are referring to essence, there are several ways.
If you need essence for a defensive tower, you should build an Essence Collector. It generates essence by burning crythilium, which is refined crystal.
Radiance Pools also (very slowly) generate essence.
When you harvest forests, crystal patches, and wild food, it spawns essence.
Dissolving the bodies of dead monsters also provides essence.
If you drop things into Cullis Gates, it provides a large boost of essence.
If you were referring to a different kind of energy...well then sorry for wasting your time :D

[Liro Raériyo]

it should also be noted that your essence bar also very slowly regenerates naturally as well

[MaebeKnot]

When you tech up enough, lightning rods are a great source of essence when it storms.