Mac keeps connecting to wrong wifi network

Whenever my mac starts up it automatically connects to a public hotspot near my house (BT-WIFI) instead of my home network. I have BT internet myself and my mac remembers my password etc, I just need to keep selecting it from the list of available wifi networks every time I turn it on.

I've gone into my network preferences and found a page where it is possible to rank the networks in order of preference after reading a few things about this online, but the problem I have is that I can't actually do anything on that screen as all of the networks are greyed out and I can't click on anything. See the attached screenshot for an example.

How can I activate this list so I can put the hotspot as low priority and my personal network as the preferred choice?

Many thanks in advance for your help,

Ben