http://work.chron.com/add-pmp-linkedin-9449.html
Adding Suffix
1. Log in to your LinkedIn page and mouse over the "Profile" link.
2. Select "Edit Profile" from the links that pop up.
3. Click the "Edit" button beside your name.
4. Enter "PMP" in the "Last Name" field, after your last name, and click "save changes."
Adding Certification
1. Log in to your LinkedIn page and mouse over the "Profile" link.
2. Select "Edit Profile" from the links that pop up.
3. Scroll down to where it says "Certifications" and click "Add a certification."
4. Enter "Project Management Professional" in the "Certification Name" field and "Project Management Institute" in the "Certification Authority" field. Select the dates for which your certification is valid. Then click "Add Certification."
