A couple of methods actually. The profile needs to be public and you need to have "manager" rights to it or collaborate with someone who does.
1. Upper right hand corner next to "follow" button - Options button - drop down - Add to Project - select Project.
2. Or at the bottom of the profile next to the immediate family module there's text - Related Projects - There are currently no projects tagged with xxx. Add to project (hyperlink, drop down)
3. OR easiest yet! Join the Project as a collaborator (which you can for yourself after you "follow" it). Go to the Project "front page," select Options - Add Profiles (dialog box) - Type the first or last name of the person you want to add. In this case profiles you follow and even those you've just "recently viewed" will be available.
Very happy to see the United Empire Loyalists project, Christopher.
http://www.geni.com/projects/United-Empire-Loyalists/10580
I wonder how many of us have UEL ancestry?