I doubt this will be of interest to anyone but me, but for the sake of completeness, here's how you get started:

1. clone this repo and run npm install
2. copy sample.env to .env and fill in your login information and download path
3. run ./download.js and watch it do it's thing

Then you'll have your current balance (minus pending transactions) in the console, and a "chase.QFX" file in the download folder you specified.