How to make custom field open

-- url of the page with the problem -- : theretis.com.au/index.php/hikashop-menu-...oduct/140-cat-1-blue
-- HikaShop version -- : 2.6.4
-- Joomla version -- : 3.6.4
-- PHP version -- : 5.6.27
-- Browser(s) name and version -- : Chrome 54.0.2840.87

The fourth characteristic on the product is 'Text' radio buttons.
How can I make the 'Your initials' custom field appear only if the radio button 'initials' is selected?
Please see attached screenprint.
Thankyou

Hi,

The setting "display limited to" is made for such purpose.
www.hikashop.com/support/documentation/1...form.html#additional

Regards,

Sorry. I still don't understand what to do. Can you explain further?
Thank you.

Edit:
I might be understanding it now. Instead of "Text" being a characteristic, I create it as a custom field and then create a second custom field and limit it to the Text custom field.
This is great software but there is a steep learning curve!