If you have access to add new users for your company you will see Admin as the first option in the pull down menu under your email address.
Once on the Admin page you can simply click the button Invite New User
Enter the users Full Name and E-Mail Address, select their role (Users) and click Invite New User
The user will receive a welcome email with a link to complete the registration process.
Once they complete their registration which includes setting their password and security questions they will receive an activation/confirmation email.
Clicking the Activation link will complete the user setup process and the user will then be able to log into the site.