Husarion Cloud is the webpage which allows you to control and program your robots remotely. To be more precise, this is not only a webpage but a lot of staff working on several servers.
The Platform is a main interface between you and your robot. You can use RoboCORE without the Platform (see offline development page for more info) but this is the more geeky way :)
Ok, let's say that you will be using Husarion Cloud and you need to register your account.
It strongly depends of your hardware configuration. Please visit the How to start guide, but you have to check if roboCORE is still connect via USB with your Android device.
In general, when you add a new robot to your account, you need to make a unique connection between your RoboCORE and Husarion Cloud. RoboCORE mobile application for smartphone/tablet can generate the registration code. This code is sent to the Platform together with unique ID. If the registration code matches with the corresponding ID in Platform database, the robot can be added to your account.
Remote controlling is available via hCloudClient API. For the first time, you can use the template from the online platform.