how do set up radio buttons to allow multiple selections

For multuple selections we do have check box fields, the radio buttons, by default are used for single selection, unfortunatelly it is not possible to change this set up. You are able to set up a maximun or minimun selections in a check box field.

Please refer to the following guidelines:

https://www.jotform.com/help/251-How-to-set-up-minimum-or-maximum-number-of-selection-on-Checkbox-Field