Changed or charged, or both? After you disconnect the negative then positive battery cables at the battery, you might have a small metal bracket bolted down in front of it holding it into place. If that's there, then unscrew it. After removing the bracket, you just have to make sure to avoid any screws that are sticking up through the battery tray, as the battery might get snagged on a screw when you're trying to lift it out. If you do have a properly-sized battery in place (a BIG one) the rest is just a matter of lifting it out. It's probably a tight squeeze where the battery is located, if it's a big one, and that in conjunction with the weight of the battery might make it difficult to remove. If it's too awkward to lift out, you might want to ask somebody to help you.
These "plates" clamp down on the edge of the battery. I believe there are two 10 mm nuts that hold them tight against the front edge of the battery. Be sure to adjust your hood in the full upright position by unlocking the clips at the hinges nearest the fender. You can get better access to the battery.
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