arcgis desktop - Network Analyst: Location Allocation for Model Builder

I am trying to create a model to answer a question using a network analysis.

Background:

• 10 possible fire station locations (shapefile)


• Calls for demand points (shapefile)


• Impedance is 5 minutes from facility to demand

Product: I need to make a model to select 1-3 stations from the list of 10 for the best locations to meet as many calls as possible with a 5 minute drive from the station.

Below is an image of what I have so far, but when I try and run it I get an Error saying:

• Error 000735: Input Network Analysis Layer: Value is required



• WARNING 030036: A layer with this name exists

Not sure how to fix these two items.