STng Cabling

Trying to set up Raymarine Model E70012 to run in my house during the winter so I may practice learning to use it. Have a DC power source (safe).

Thought all I needed was to run a GPS antenna outdoors. Purchased Raymarine model RS 120. It came with 6-pin cable.

Set all up, no GPS signal. : (

Go back, learn about this STng system. Maybe that's it. Purchase two STng spur cables one long (to antenna outdoors) one short to create little mini-network. Purchase a "Backbone Terminal" and a "T" and a terminal pin.

Final part came today. Inserted short spurt to primary unit, inserted end pin in other and...discovered remaining [censored] has 5 pins, not six.

I am confused. Now what do I do?

thanks all

Henry