How do you use FastCast?

I’m using the lastest version, and I have no idea how it works. Here is the current line I have so far
Caster:Fire(Vector3.new(v.CFrame * CFrame.new(0, 0, -35)), Vector3.new(0, 50, 0), 2000, v, nil, true, Vector3.new(0, 0, 0), nil, nil, nil). Yes I have a Caster.new() line. Also those values are from me trying to see what would happen. My projectile spawns then falls, and yes I checked the API.