There are many brands of Wifi amps. I use one extensively and it has a 30 foot long cable. The antenna box is 4" X 3" and I position that somewhere in my RV where it has the best angle on the parks Wifi antenna. If you have a PC, tablet, or laptop, you just plug the device into a USB connector on the computer and these days nearly all OS's will auto connect to it. Here's one from eBay:
Long Range Wifi Antenna
Often I'll end up with the antenna taped to a window. I often route the long cable on the floor under rugs, or have it taped to ceiling fixtures. It's a travel solution so I didn't mount it permanently outside but that can be done of course. Like attached to the rooftop gull wing antenna.