This will be largely familiar territory to anyone who has already created projects for iOS, with just a couple of things to bear in mind, which will be pointed out as we go along. Do note, however, that if you have not yet updated to Xcode 7 and there are many professional environments in which updating isn't done without a significant degree of caution—then now is the time to do it, Xcode 6 will not build WatchKit apps beyond the first version of watchOS and we will be developing for the vastly superior watchOS 2.
Assuming you have Xcode 7 up and running, we will now let it do much of the work involved in setting up a project that will include the targets, schemes and source files needed to create the basics of a Watch app and its companion iPhone app.
iPhone, by the way, not iPad. Only the iPhone (5 and above) can pair with the Watch, and if the app is run on an iPad, the presence of the Watch app will simply be ignored.
A template is provided...