sign up
verb
Definitions
To add a name to the list of people who are participating in something.
Example: We signed up Bob for kitchen cleanup duty.
To add one's own name to the list of people who are participating in something (including amateur, but not professional, teams)
Example: Terry signed up for the soccer team.
To agree to purchase some good or service.
Example: After much deliberation we decided to sign up for satellite TV.