Remove the battery.

Be sure to remove the protective liner to expose the adhesive on your new battery before you set it in place.

If needed, try re-using the existing adhesive to secure the battery. Alternatively, try a small piece of double-sided tape such as Tesa 61395, or a dab of liquid adhesive such as E6000.

If you're using an iFixit repair kit, proceed to the guide linked in the conclusion below to install a new Force Touch sensor and re-seal your watch.

Alternatively, if you are just replacing the adhesive and not the sensor, see the adhesive replacement guide for applying new adhesive and then reassembling.