A User is sent Verification Request when their account is created to verify their account against their email account. There is a 3-month expiry on the Verification so if the User has not verified their account in this time they may need to be sent a new Verification Request.
Click on the launchpad in the top left and then the COG to access the Settings area.
In the settings area select the 'Pending Users' App to bring up the list of pending Users on the site. Find the User that you would like to send the Verification Request to and click on that User to open their User profile. From here, use the feature menu '...' and select Resend Email to bring up the confirmation pane.
When you click on confirm, an automated email will be sent to the User asking them to Verify their account - which will once again have an expiry of 3-months.
For information on how the User can then verify their account, refer them to this article on Verifying your Softools Account
Note: Once a new Verification Request has been sent to a User it will invalidate any previously sent Verification Requests.