How do I change the icon from the Font Awesome library?

Hi Dan,
Welcome to PickPlugins.

First, go to the Edit mode of your accordion.
Screenshot: https://i.imgur.com/7W9qqgR.png

Under Style, you can set any font-awesome icon for Active and Inactive icons. Just make sure the icon is from the font awesome version 5.
Screenshot: https://i.imgur.com/SCpt3gU.png

To grab the icon code, visit this URL and look for your desired icon -
URL - https://fontawesome.com/v5/search
Screenshot - https://i.imgur.com/GkBSeun.png

You can find and copy the icon-code after clicking on an icon.
Screenshot: https://i.imgur.com/goirUC2.png

Finally, paste the code under the Active or Inactive icon input.
Screenshot: https://i.imgur.com/GIGETNz.png

Let us know if it helps.

You can join our Facebook group to resolve any issues. It's open 24/7, We have got a helpful community. You're welcome.
Facebook group: https://www.facebook.com/groups/PickPlugins