You can add custom fields to your password entry, by going to the Custom Fields tab while adding or editing a password entry.
Click Add to create a new field. In order to do this you have to enter a name for the field and the value which the field should have. If you check the option Visible in top bar, this custom field will appear in the top bar and you will be able to insert it from there directly.
Click Edit to change the value or the name of a field.
Click Delete to erase the selected field from the list.
Use Move Up and Move Down to change the order of your custom fields.
If you uncheck the option Mask Values you will be able to see the values you entered for each field.
Click OK when you are ready.