How to store selected data from a dynamic list

You have many options and it depends on what you are trying to achieve. You could use a list control: check box list, radio button list, drop-down list, choice control, list box, list display, look up, even a list view.  Each of these controls will have a data source property that uses a SmartObject to return the dynamic list of values.  The control itself can be bound to the SmartObject where you are saving your data for the view.  When the control is bound to a SmartObject, its value is saved or loaded when add the appropriate rule to load or save.

Here is some information from the product help site that tells how to configure a datasource for the control: Check Box List Control (nintex.com)