Requirements: 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 you can click on the Manage tab to see information on the organization users.
From the Manage tab, you can access your Users as well as Pending User Invitations.
If you would like to get a list of all Users within an organization, you can 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.