Step 1: Once you have added users, and sent activation invitation emails, you'll see that their status is 'Activation Required'. You will also see an orange dot next to their name.

 

Step 2: Click on the three dots to open the menu, and click 'Send Activation Reminder'.

 

Step 3: If you'd like to send bulk reminders, select the users you'd like to send the emails to. The 'Bulk Actions' button is now clickable.

 

Step 4: Click 'Bulk Actions' to show the dropdown, and click 'Send Activation Reminder(s)'.