NOTE: You will need to be an Organization Administrator or System Administrator to access this information (see User Roles in Bonfire for more info on these roles and their privileges).
Once you have signed into your organization's portal, click on the Manage tab to see information on the organization's users.
From the Manage tab, you can access the Users section which lists all users from within your organization that are on Bonfire.
If you would like to export a copy of this list, simply select all of the text on the page and then copy and paste it into an Excel document. Keep in mind that this may require some formatting to be done, but will allow you to generate a list of all your organization's users.