When you see the Register a colleague button under I want to help, you can register a member of your team to the same opportunity as you.

The Register a Colleague window will appear,

You can also register friends and family using this button if allowed by your organization. Make sure you can click on No for the question Is the person you are registering an employee of your company?

If your registration is successful, you will see your team members name under Registrations on the Opportunity Page.

Your team member will receive an email in their inbox to let them know you have registered them.