How to connect keyboard and mouse to mobile?

The easiest way is with Bluetooth, for sure. Just go into your phone's Bluetooth settings and pair them up. It's heaps easy, just like connecting speakers. If your keyboard and mouse use a wire, you will need a special adapter. For Android, it's called an OTG cable. For an iPhone, you need a Lightning to USB adapter. You just plug that in, then plug your gear into the adapter. It should work straight away.