Quickly looking at my Lucid I don't think it can be done. But normally its part of the contact it self when you go to edit the contact. Maybe something that I am missing if you want to look at it farther.
It should be an option under the individual contact in the Contact App. You might have to check under the menu button for more options.
I'm most definitely NOT a VZW employee. If a post answered your question, please mark it as the answer.
Open the contact. Open the menu, select options. Ringtone is the first option. Open ringtone and a drop down box with available ringtones is displayed.
If you want to add your own ringtones of music you have on your phone open music player in your media apps. Slide the menu bar at the top of music player and open the folders icon. Open the saved music folder and touch and hold the song you want. Select the use as ringtone choice. The song should now show up in your ringtones.