Crystals should be cleansed upon purchase to "reset" them. You want them to specifically serve your intention, and not to be clouded with past energies that they've picked up along their journey to you.
Cleansing your crystals can be done in multiple ways. Some traditional ways of doing so are with sage, incense, moonlight, and water (not recommended for these bracelets though!)
The process is easy:
If using sage or incense, pass your crystal bracelet through the smoke a few times. While doing this, you want to be focusing on wiping the crystal clean of it's past energy. Envision this in your mind, along with white light or whatever else represents purity to you.
Now, another awesome way to cleanse/charge your crystals - under the full moon! I love this one because it's so easy and I love the idea of the moons energy pouring into my crystals. So, all you have to do is leave your crystals out under the moonlight :) I sometimes leave mine outside in the summer, but I don't recommend this if there's any chance that someone could take them. Another option is to leave them on your windowsill. This will have the same effect as the sage/incense method, and then you are ready to move on to the intention setting.
The Intention Setting
After you have passed the crystal through the smoke or charged them under the moonlight, you must now program it to your own specific intentions and desires. I recommend that you go into a sort of meditative state for this. Sit quietly with your crystal. Hold it and picture what you wish it to bring you/help you with. If you are into the law of attraction, that's kind of how this works. You want to feel the positive emotions you are trying to manifest as vividly as possible. Once you feel as though you have set the crystal to your desires, you are finished.
Now you are ready to rock! No pun intended ;)