Get a plastic pry tool (recommended) or a small flathead screwdriver (only if pry tools are not available).

Find a space inbetween the bottom and top section to put your pry tool into.

From the first section, work your way around the laptop, prying up each plastic tab so it clicks out of place.

Make sure to be careful around the hinge as the battery is positioned around that area and could be punctured or damaged if you're not careful.

If you are using a flathead, make sure to keep the screwdriver relatively vertical as to catch onto the tabs as they can be quite tricky. One trick is to push it straight down and then angle it until it's horizontal, after this the plastic tab should come undone.