Remove the battery.

Do not reuse the battery after it has been removed, as doing so is a potential safety hazard. Replace it with a new battery.

Remove old adhesive backings before installing new adhesive and clean the relevant areas with isopropyl alcohol (>90%).

If your replacement battery doesn't come with replacement adhesive, secure the new battery with pre-cut adhesive or double-sided adhesive tape (OEM adhesive is a 32x32 mm square). In order to position it correctly, apply the new adhesive into the device at the place where the old adhesive was located, not directly onto the battery. Press the new battery firmly into place.