The Counting LoopStart is the node that starts a loop which is executed a predefined number of times. At the end of the loop you need LoopEnd, which collects the results from all loop iterations. All nodes in between are executed as many times as you specify in the dialog of Counting LoopStart.
The input ports are just passed through to the output ports. You can add an arbitrary number of port pairs by using the “…” menu.