Thing you will need: Your Device
USB Flash Drive
1. Go to the play store and download an app called OTG Disk Explorer Lite. This app might not work for all people. If it does not you can use Nexus Media Importer(Google Play). One can also use ES File Manager.
2.Connect the OTG cable to the device and connect your USB to it.
3.Open which ever app you have downloaded .
4.You can now view files on your USB.
Note:You can also use a card reader and externally powered portable HDDs.