To add a profile picture to an existing constituent or non constituent record please follow the steps.

1.  Select a picture and drag it to the empty space on the constituent profile.

or 

1.  Click on the empty space on the constituent profile
2.  You will be prompted to choose a picture from a file location
3.  Click save

*Note* A constituent without a profile picture will default to their initials and a random color background.  There is no way to change the background color that appears.