sign up to something

Từ điển Oxford Advanced Learner 8th

ˌsign ˈup to sth derived
1. (BrE)to commit yourself to a project or course of action, especially one that you have agreed with a group of other people, countries or organizations
•How many countries have signed up to the Kyoto protocol on climate change?
2. ~ to do sth to agree to take part in sth
•We have about 100 people signed up to help so far.
Main entry: ↑sign_derived