In the detailed view of any contact profile, you can edit or add information to the Personal section.
Simply click on the pencil icon to open the editing screen:
Type in the information you wish to add, and click add.
This will now update the data field on the profile.
If you would like to update or amend information, simply add as detailed above. You can then remove the irrelevant data by clicking on the x icon next to the information you no longer require.