If you have Admin Rights for your organisation you will be able to find the Admin option in the top menu panel. In the Admin panel you are able to manage Users within your own Organisation and approve or delete Pending User Requests
In Users, you will find all Users registered under your organisation as well as any Pending User Requests for your Organisation. You can either approve or reject these requests. You can search users by their name or e-mail address. You can also promote a user to an admin and demote them to a normal user. The X in the far right will delete the selected user.