This feature is part of the Visforms Subscription and not available in the free Visforms version..
Please make sure, that you have installed your Visforms Subcription. After that, you can use the new function directly. Go to the menu manager and open a menu item of type Visforms Formdata. You will find a new option "Display Searchbar" under the tab "Form data display options".
Set this option to "yes" in order to display a searchbar in the data list view.
Visforms will create autmatically search filters that fit with your form and field conguration and the settings for the frontend data view. For each field of type select, radio, checkbox group and checkbox, that is displayed in the frontend data list, you will find a select with all allowed values for this field in the search tools. All other field types can be searched using the search box.
If you have published submission using the content plugin data view, you have to use the proper plugin parameter in order to add a search bar to the frontend data view (see: Parameter list).