Small router for mobile coverage not linked to main router but stand alone

[northwest]

I am using the wrong terminology but I had someone here today sorting out my laptop and he said that the main broadband router should be linked by cable to the smaller one and that the latter should be fitted with antennae. 
he said at the moment it is just plugged in and wasting electricity. I think the smaller one is meant to be used to access mobile coverage if the Wi-Fi goes down. When the EE engineer set it all up should he have done this too? I am on a full works 36 package. Any advice is appreciated. I am not aware at any point of being provided with a cable or with the antennae. Many thanks.

[XRaySpeX · Accepted solution]

The smaller router is a 4G mobile router called Smart Hybrid Connect. It is connected to the main BB router by cable which comes with it & is intended to automatically provide a connection if your home broadband goes down. No antennae is provided or needed.

See Set up Smart Hybrid Connect

[northwest]

That is so helpful. I think from reading the links you sent that the engineer must have paired it using the wireless without needing to use a cable. It is showing two bars for a signal so must be paired. Thank you for the information. 

[northwest]

I can see you replied saying you are not sure it can be paired via WI-FI- I think that is what the guidance says ( that you can use the EE app Ethernet cable or Wi-Fi) but just to be sure I will take photos and pop into my EE shop when next nearby. I am sure they can provide the right cable if that is what is required. 

[XRaySpeX]

Yes, that's why I removed my post after fully reading the Guide.