K3 Pro battery replacement help

I have had the model K3P-B3 for around 3 years now, and the battery has been lasting less and less.

I found the battery I need and ordered it online. Now that it has arrived, I am concerned about how I will be able to put the new battery in, after I take the old one out.

The reason is that all guide videos I watched only show how to take the battery out, but not how to put one in. Specifically, I see that they take some sticky plastic off the battery, that used to hold the battery in place. Does that mean I need to stick my battery back to the plastic part? Thanks.

Example:
https://www.youtube.com/watch?v=SPqu8REdmuA