Where can I find RPC_User and RPC_Password for my Python Script?
To use this library you need an instance of Bitcoin core!
If you start with Bitcoin I suggest you to run an instance of bitcoin core and understand how the config it. You can find a good start here!
In addition, to use the lib inside your question you can following the steps below:

Download Bitcoin core and run an instance of it, I suggest you to run Bitcoin core on testnet, because it is not a small instance of &quot;real&quot; bitcoin network
Config Bitcoin core with a conf that accepts the connection on RPC!
With the RPC username and RPC password, use your code to connect to the Bitcoin code RPC interface.

Good hacking!