Download the iOS agent source code. For more information on the agent version related to the IoT Server version you are using, see WSO2 IoT Server and Agent Compatibility.
Build and export the project as an iOS application using Xcode. This will generate an ipa file.
Sign in to WSO2 IoT Server's App Publisher console: https://<IOTS_SERVER_HOST>:9443/publisher. The default username is admin and the default password is admin, and the default IOTS_SERVER_HOST is localhost.