hey sorry man - this was done a few years back when I had my business office in my spare room at home. I had no internet / cell phone signal whats soever.
I ranted and raged on the phone to mtn and they sent out a techie who did a field test and then installed the yaggi antenna free of charge.
it does not plug into anything - it just has a flat pad that I put the usb internet dongle on with an elastic band. I also used to use it with my phone as I'm on the fringe of the cell tower and prior to the antenna being installed my signal used to "float" around and caused many dropped calls!! customers used to complain

I then discovered that there is one spot that I get a good usable signal and that is by my wash up in the kitchen. :wtf:
I've used this setup for years now and I just assumed I could just do the same with the MiFi dongle. without the yaggi antenna the signal is orange - once I've put the MiFi on the yaggi pad the signal goes all green!