Use ListBox to add multi-select functionality in the app.
Enter a Label for the ListBox tool. This is the name of the tool in the app.
Select the Label Source. This is the name of the column that holds the text that you want to display.
Select the Value Source. It is automatically populated as per the selected Label Source. You can change it manually if needed.
Select Check All by Default checkbox to select all the values by default in the app.
Select Save.