How to use Roblox's Pathfinding service?

So I am making my own zombie and I of course need pathfinding for it. I tried to make it in the past and it didn't work too well. I just wanna know the proper steps for pathfinding because I think I may of missed a step when I was making my zombie.

I just need to know how to use pathfinding and I need to know when I'm making a npc that where I should I use it. Do I compute a path in a while loop everytime to make the zombie's path stay updated?