How do you add an online certificate to LinkedIn?
The short answer
Add it under "Licenses & certifications" with the issuing organization and the certificate URL. LinkedIn Learning and Coursera do it in one click. Also add the skills you learned to your Skills section, because that is what recruiters actually search on.
In detail
A certificate nobody sees does nothing for your career. LinkedIn is where it becomes visible, and most platforms make it easy. LinkedIn Learning has a built-in button, Coursera and edX provide a shareable certificate URL with verification, and DataCamp and Codecademy issue shareable certificates too.
The right spot on your profile is Licenses & certifications. List the certificate name, the issuing organization (pick the official company page so the logo shows), and the verification URL. More important still is the translation. Add the concrete skills (SQL, Python, project management) to your Skills section, because recruiters filter on skills, not course titles.
The best presentation is not the certificate but the result. A post sharing what you built or learned, project included, does more than a quiet profile update. And stay selective, because five relevant certificates look stronger than thirty loose badges.