there’s noplace to configure dropbox

Hi @juliakline
you can always open a support request from our forum here and we and others would happy to help you with your issue ^^
https://www.ads-software.com/support/plugin/backwpup/
About your issue, you can create a new job -> scroll to Job Destination section -> tick Backup to Dropbox.

After that, follow our official instruction here: https://backwpup.com/docs/backup-wordpress-to-dropbox/

Also here is a detailed video tutorial recorded from others about how to setup BackWPUp with Dropbox: https://www.youtube.com/watch?v=WecrXv_7ALA

Basically it really easy too, anyone can do that ^^