Nav 2016 Phone Client - adding field

Hi ,

Struggling to figure out how at add extra display fields on the phone client. For instance, if you look at the customer list, it by default shows the customer no., name and contact, but say i wanted to add an extra field to show (for instance balance), how do i do that?
At first i thought it might be through Bricks, but it doesn't seem to make any difference.

Thanks