This is one of the most simple spells of them all. For charging, you might want to cleanse an item first (See the previous spells) to ensure whatever you want to charge them with stays with no obstacles.
You have two choices:
Charge them with the power of the moon.
This goes for any object related to both earth and water, also, for those items blessed by the goddess. What you have to do is take the object outside and leave it under the light of the full moon. Now, depending on what you want them to do, you can choose another phase of the moon. Let’s say you want to charge some tool that vanishes evil energy, you might want to charge it during the new moon (Or a lunar eclipse) so it wipes away things, on full moon for something designed to find lost items or give light, etcetera. It’s a matter of research.
Some people prefer to leave this objects in a small outdoors altar with a few charms. Protection spells, barriers and cleansing spells can help you to ensure that, while your object is soaked in moonlight, no evil energy is going inside it.
Charge them with the power of the sun.
Any object that has a relation with Fire and Air will probably have a better energy if you leave it a few hours under the sun, or if you leave it from Dawn until twilight. Be careful with some crystals and items, since some of them fade with intense sunlight.
You can, as said before, protect your object with any other charms or rituals you want to perform to ensure no negative energy comes into it.