You can create a new Ad on Newsfeed by clicking on "Create new Ad" button at the top.
The popup will show up where you can select an Ad host (your profile), type an Ad title, select an Ad image, choose an Ad plan and type a short description of your Ad.
Creating a new Ad is not free.
Note: In order to create a new Ad you have to have at least one profile because all advertising goes through profiles. You can create your first profile for FREE.