As Tood Wilcox mentioned, I also use a footswitch connected to my Ableton Push to control track record/start/stop so I can play and record guitar without having to use the mouse/keyboard.
But if you don't want to buy an additional Push/Keyboard/MIDI device to use with your FS-1, you can get a standalone footswitch that plugs directly into your computer via USB. Search for "USB MIDI footswitch". There are plenty of options. Most of them have a few different switches, but in Ableton you can map any MIDI input from a device like this to any number of parameters.
It looks like your Scarlett doesn't have direct MIDI input, so if you can't find a USB MIDI device, you can also use regular MIDI device with an inexpensive MIDI>USB adapter (about $20). One popular MIDI pedal is the Behringer FCB1010, though it's about $150. There are cheaper options as well.