Unfortunately, your site needs to be secured. There's no way to override the HTTPS requirement unless you override the /ssc/auth route and use your own login mechanism.
NOTE: I don't recommend below but if you MUST really not have HTTPS...
You can do this by updating the
Sitecore.Services.RouteMapper setting in the
Sitecore.Services.Client.config. Reflect the
DefaultMapper and override the
MapRoutes method that defines the "auth" route. You'll notice that it's pointing to
Sitecore.Services.Infrastructure.Sitecore.Mvc.ServicesAuthenticationController. So, you'll need to copy that and essentially remove the
"RequireHttps" attribute on the
Login method. Point your new auth route to this new controller.
With regards to more details on the SSC, you may want to check the 7.5 documentation as it has a lot more examples. Most of it still applies.