Take the thinnest possible tool, and slide it into the gap between the two parts of the earbud’s shell.

Then, start to lever the two halves apart at the point circled in the picture.

If the two parts don’t separate, you’ll need to heat the earbud a little more.

When the two parts of the earbud’s shell start to separate, continue to separate them by levering all around the shell.

Careful not to burn your fingers as the earbud will be very hot.

In the picture I used the iFixit’s Jimmy opening tool, but I think the iFixit’s iFlex Opening Tool is better because it is thinner so it might make this step a bit easier.