Hi @Priyabrat Swain ,

For this you needed to created a list record. There you needed to add a  checkbox or radio button based on the no of user you want to select.

Please check the link below for reference .

Sample 1

Sample 2

Thanks and Regards

Pranav 

Step One - You have to add user aggregate on the screen 

Step 2:- Add a radio group and take only one radio button 

Step 3:- Make local variable user identifier type 

Step 4:- bind Radio group variable to that user id variable 

Step 5:- Bind the radio button to list the current user ID

Are you sure a radio button list is a good UX behavior for this situation? It works nice up until around 5 to 8 people. Then the list gets to large. Perhaps you should better use a dropdown as this is more suited for a selection from a large list. If you use the new DropdownServerSide you even have search capability.