Do you have low shower head pressure?
A leaking tub spout could be your issue. Replacing one can be a little channeling especially if it’s been there for a long time. And for most of us, it has. Running very hot water first should help with removing it.
Once you have the old one off you’ll want to clean the threads up. Just remove any debris and old Teflon tape and install new Teflon tape. And it’s really simple to install the new one. Just screw it on, Clockwise until it’s lined up and snug. It’s that easy.