Most laptop CMOS battery's are just under the keyboard, usually you just have to undo a couple of screws on the underside of the latop to remove the keyboard. These screw are usually marked differently or have a symbol on the casing next to them so you can identify them.
Just beware that when you lift the keyboard it will usually have a quite delicate ribbon cable with a small block connector that you'll need to pop off the motherboard tp completely remove the keyboard.
Easier than it sounds, honest

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