The simple IoT Client can be downloaded from: https://github.com/PeterWaher/IoTGateway#clients
For source code examples of how the owner interface is implemented, see https://github.com/PeterWaher/IoTGateway/blob/master/Clients/Waher.Client.WPF/Model/Provisioning/ThingRegistry.cs.
When you open your IoT Client for the first time, you need to create a connection to an XMPP broker. This is done using the
Connect to... command (the star icon). That allows you to create an account or connect to an existing account on an XMPP broker. Connect to the same broker your devices use, so that you can automatically use the same Thing Registry and provisioning server.