That doser will draw very little current so I would put it on one of the relay outlets and program it to be turned off if your pH gets over 8.4, that way if the doser fails and tries to OD alk the apex will shut it off.
If you sign up with
http://www.reeftronics.net/ you can see and use other peoples programs and reeftronics has diagnostics and monitors your apex to verify it is communicating and will email you if it's not.
It's a little late now but myself and others here, i'm sure, will help with some programming. Just be patient and get things up and running one thing at a time, once it is set you will be worry free. I would start with programming the heater.
Also the apex forum has a lot of info.