From your list of users:

• click on a user name to open the account details (or right click on a username to open the account details in a new browser tab)
• check they are eligible by looking at the details on the account tab (check email address, name of trust, postal address, etc)
• if you decide they are eligible and in your organisation, go to the top right hand corner of the screen and click on the down arrow next to Actions:
   
   
   
   
   

•  choose Approve/reject registration requests and you will see this screen:
   
   
   
   

• click the green Approve button. 
  
  An email will be sent to the user unless you untick the box.