In order to change the owner of a function, click on the checkbox to left of the function name and click Change Owner. Upon clicking Change Owner link a popup will appear that shows all of the users to whom you can assign the selected function to. Once you select a user from the drop-down presented and confirm, that user will become the new owner of the function. Only owner of the function and a user with admin role can perform this operation.
You can alternatively click on the Function Info button to get to the function edit screen
Then select a user from the Owner drop-down presented below and hit Save.