To connect your ORCiD account to CrossRef Metadata Search, first select "Search and Link" from the options in the "add works" dropdown in your "works" section:

Select "CrossRef Metadata Search" from the following list:

When presented with screen to Authorize the Trust Relationship, be sure to click Authorize. This allows ORCiD and CrossRef to communicate with each other. CrossRef is the only database that will push new publications into your ORCiD account, so this step can be a large time-saver as long as you include your ORCiD ID number on future publications. 

It is not recommended to search by name in CrossRef, as name searching is imprecise. However, many books and book chapters are indexed in CrossRef and can be found by searching for just the title of the book in quotations. Once found, just click "Add to ORCiD" in the record.