Hey Jessica -
However, wondering if anyone has used Shopify FD as I can't seem to find a manual or anything.
There's around of 6500 people that use the tool (plus a bunch with their own custom version) so there's plenty out there. One thing that I've not made is a user guide or manual so it makes sense that you've not found anything.
If there's something you'd like to see in user guide let me know what that is. Always ready to take feedback and suggestions on the tool.
FYI: There's a giant thread for the tool here, and if you find a bug it can be posted here.