✓ Accepted answer
Simply put, setting Focus when CameraType is set to Scriptable will do nothing. What you can do is make the camera's CoordinateFrame start at one point while looking at another. To do this, you can use a built-in CFrame constructor:
CFrame.new(start, lookat)
Where start is the position of the CFrame and lookat is where the CFrame "looks" at. Both must be Vector3. To use this in your script, you would do something like this:
cam = game.Workspace.CurrentCamera
cam.CameraType = "Scriptable"
local start = Vector3.new(-15, 5, 2.5)
local lookat = Vector3.new(20, 3, 2)
cam.CoordinateFrame = CFrame.new(start, lookat)
wait()