How do I allow users to edit the 'Ticket Type' and 'Priority' fields when submitting ticket?

In order to allow end users to select Ticket Type and Ticket Priority when submitting a ticket, they have to be made public. You can make them public from the following settings: 

For Ticket types:Admin CP -> Tickets -> Types -> Select the Type -> General tab -> Visibility: Public.

For Ticket Priorities: Admin CP -> Tickets -> Priorities -> Select the Priority -> General tab -> Priority type: Public.