To use the RunCam HD App, you need to buy a OTG Adapter firstly:
http://shop.runcam.com/micro-usb-otg-adapter-data-transaction-for-runcamhd-android-app/
But you need to know firstly if your mobile phone will support the OTG function, it depends on the brand and the type of your mobile phone.
And if you want to know more details, please see this video for refference:
https://www.youtube.com/watch?v=ARawKx85r-U
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