How to connect a web app in a pc with a database on another pc using php mysql XAMPP

Question

I have a web app in php mysql programmed with xampp server.

I need to have the web server with the app files in one pc on xammp and connect it to a mysql database on another pc using xampp also I imagine on phpmyadmin as usual.

I don't know how to redirect the database, as in one pc you just put the dB name in the queries but I don't know how to do it if the database is on another pc.

I couldn't find any info online, I already can access my xampp server through ip address on another devices but with the web server and the dB server on the same pc.

I need to have the web app files in one pc and the database in another, using xampp in both pc. So I can connect other devices as clients and use the web app normally.

Please help:( it is for a project :(

Edit: I am beginner, so I really would like a detailed explanation with examples please so I can replicate it.