This guide will let you know how to Make & Delete paths in Two Point Campus
You will need to open the menu on the bottom left by pressing the square on the PlayStation or by pressing X on the Xbox. Go to the tree icon and then press the r1 on the PlayStation or the right button on the Xbox.
It will bring up the Path and Terrain window.
And then you can do exactly what you do with the rooms. You can just place it down as normal and then if you want to delete it, you have to press Square on the PlayStation and X on the Xbox.