What you want to do is actually quite advanced topic. Godot is coming with some build in functionality that you can use Look for navigation mesh
But if you never used a game engine I recommend you start with baby steps and lern how Godot works basically. Try to create a scene, create an object, add a script and try to move it from code... All this stuff.
I would recommend to at least completely the getting started section of the Godot docs this should give a very good overview.
What? Creating a nav mesh and copy pasting a script for the agents to move it will also just take a few minutes... It's just that if you want to know what you are doing this will take you longer.