Remove first cover by carefully prying (e.g. with an old (credit) card)

It should not take much force

In the created opening, roughly where the red square marking is, there is a small plastic latch/hook.

Lightly press it down and pry on the back cover with the bluetooth logo.

This is the hardest step. Be patient and careful.

There is two more latches/hooks, these should not pose a big problem once the first one came lose.