You may want to review the multiple accounts per service FAQ.

Thank you for directing me there! Was hoping it would help but the page shared that “Adding another music service account follows the same process outlined in our Add a music service to Sonos article.” I’ve also checked said page but it only highlights how to well, add a music service. However, I’ve already done this and simply need to find out how to add multiple users. Any other advice would be greatly appreciated!

You just add the new account to the service as indicated in that other FAQ. If it seems confusing, it may be easier to do from the other person’s device, but you then get the pull downs as the article suggested. 

You can always call Sonos Support directly to discuss it, and they’ll walk you through the process.