This is the documentation for the Textboxes user interface dialog:
https://msdn.microsoft.com/en-us/library/e04k6f53(v=vs.100).aspx
The identifier EDITA1 (and others) is a property name that you can use later in (for example) custom actions. Without knowing exactly what kind of custom action you might be thinking of it's hard to say how you use it. In general, specifying it as a parameter to the custom action as [EDITA1] will cause it to be resolved to its actual value. But if you just want to store the values in the registry you'd create a registry item with the value [EDITA1].
To start the service in Visual Studio setups that install services with installer classes you'd need to overwrite the Install method, calling base.Install() and then adding code to start the service. Similarly at uninstall or upgrade time you can override the Uninstall method and stop the service before calling base.Uninstall().
These posts have some Textboxes examples:
Overriding "Textboxes" dialog fields from the command line in MSI installer (Visual Studio 2010 Web Setup)
Setup Project: user enters a value then store it in a text file or database
Visual Studio setups are not very useful with services and UI. There is no way to validate what the user enters at the time it is entered - if you validate it with a custom action it will be at the end of the install and the entire install will fail and roll back. Windows Installer has built-in support to start/stop/delete/install services but VS setups don't use it. If this is something you do regularly it might be useful to consider another tool, and that might have a learning curve but the resulting MSI will be more reliable and easier to use.