How do I add my ORCID to papers authored by myself? I have a few papers that have already been accepted and published.
I recently signed up for an ORCID.
Is is possible to add my ORCID to these already published papers,
and if so, how do I do this?

Response to comment
Ideally, I would like my ORCID to be listed on the paper itself or on the official website of the journal article.
Nevertheless, I would consider having the paper listed on my ORCID profile to be a good partial solution.
I don't know if it is possible to add your ORCID directly to the paper in question (probably not), but it is possible to link to the paper from your ORCID profile.


Go to your ORCID account (signing in if necessary)
This should bring up a page with your "Biography", which consists of several collapsible tabs (Education, Employment, Funding and Works).
Next to the Works tab, click on the button for "+ Add works". 
You then have several different options to proceed. The quickest is "search and link" which allows you to search a database such as PubMed or CrossRef, find your paper, and add it to your profile. I won't go through the full details of each step, but if you follow the instructions on screen, it should hopefully guide you through.