When you arrive on Linkedin you find the menu bar on the top. The second menu is a drop down menu, (click for it on tablet) where you can find two sub menus, the "Edit profile" and the "Who's viewed your profile".
I start here with "Edit profile".
As you can see there are some pencils on the page here. Use them for editing text.
On the left you can find some stripes with Test score etc., where you can see a + sign. Those signed with + can be added to your profile.
In the center of the picture you will find a square and a + sign, that could be used to add media (video, pdf, doc, scribd, slideshare, etc.) to your profile.