There are multiple ways to populate your ORCID with your publications.
1) Allow trusted organizations to add publications on your behalf.
You can grant organizations and publishers long-term access to add publications to your account on your behalf. This is usually tied to a manuscript submission or grant reporting workflow. For example, you might submit a paper to a Nature journal, and authorize them to connect and update your ORCID account. When your paper is published, the paper is automatically linked to your profile.
2) Import works from other systems.
ORCID connects to many research databases to import search results for your name.
From your profile page, scroll down to Works and click "Add Works." Then click "Search & link."
This expands a list of available databases to search. Choose the ones that are applicable to your field. In general, you may want to check CrossRef, ResearcherID, and Scopus. If your research would be in PubMed, you can check Europoe PubMed Central.
Each database interface will look slightly different, but all will provide a link next to each resulting citation that will add the reference to your ORCID profile.
3) Import works via BibTeX (most reference managers like Zotero and EndNote can export BibTex).
If you have an existing collection of references in BibTeX format, it is possible to import them directly. Most reference managers (such as EndNote) allow for BibTeX export.
4) Add works manually.
This is generally not recommended due to the risk of human error, but will do in a pinch.
From your account settings page, scroll to the bottom of the screen until you see Trusted Individuals.
Enter the ORCID number, email, or name of the person you would like to have permissions to add references to your account, and click search. Note that they will need to have an existing account in order for you to add them to yours.