Follow these steps to add a picture to a family or individual profile.

Step 1:
Open Membership Pro and if needed click the "Main List" button on the toolbar to display the main list of family records.
Step 2:
In the main list find the family you want to add the picture to and double click on their record.
Step 3:
When in the family record click the camera button on the toolbar.
Step 4:
With the empty portrait box open right click in it.  From the menu click "Select Portrait".  Browse to the location on your computer or network where you have saved the pictures.  Click the picture for this family and click the [Open] button.
Step 5:
Now the picture is added to the family profile.  Just click the green check mark on the toolbar to save the family record.