First, press the download button below. Your browser should download "CameraSystemV3.rbxm".
Open a place in Roblox Studio (where you want the cameras to be) and drag the file you downloaded onto Studio.
Change the settings and commit the script if you're in team create.
Download the system from step 1 of the "Installation" section
Delete the (old) camera system parts from Lighting, ReplicatedStorage and StarterGui and rename the old Workspace part to "CameraSystemOld"
Import (drag) the new camera system into Studio, delete the static/moving cam example and default cam, copy the command from here and paste it into the command bar (View > Command Bar)
Delete "CameraSystemOld"