Use the plastic card to lift the battery cell out of its housing and remove it.

During reassembly:

When installing a battery cell, make sure its cable goes into its cutout in the housing.

If your new battery cell comes with pre-installed adhesive, remove the plastic backing and firmly press the cell into place in its housing.

If your new battery cell doesn't have adhesive, use strips of double-sided tape such as Tesa Tape to secure it in the housing.