There are probably 100s of threads about the Libre - patches and straps to cover it (some use Tegaderm, some use a 3D printed strap from eBay, many of us need nothing) and what are the limitations. It works fine in the shower. The Search function at the top right of the page will help you find these.
I recommend you read up on the limitations because you will be very disappointed if you expect it to be 100% accurate all the time, right from the time you apply the sensor.