You have several options for changing the font used in a field...
Option 1
1) Click on the field you want to modify.
2) In the Properties panel, locate the Font Name drop-down menu and select the font you'd like to use.
Your font choice will be applied.
Option 2
1) Click on the field you want to modify.
2) Select the font you'd like from the dropdown menu located on the toolbar.
Your font choice will be applied.