Before running on mobile device, make sure the project is optimized to consume minimal resources. It is recommended to create a Mobile render path in Properties - Render - Armory Render Path. Additionally, simplifying materials, textures and geometry may be needed. To run on the lower than the maximum available resolution, set Armory Render Path - Post Process - Resolution property.
Create a new preset in Properties - Render - Armory Exporter and select iOS (C) target. Hit Publish to generate iOS project files.
To proceed, install XCode. Launch XCode by opening the generated project located at blend_file_location/build_projectname/ios-hl-build/projectname.xcodeproj. Connect your iOS device and press Run.
Note: Armory will target gles3 by default. If you require gles2 support, enable Legacy Shaders option in Armory add-on preferences.