Connecting USB flash storage to your Android phone is easy and cheap. Here's what you'll need:
1.A USB OTG cable
To check that your mobile Supports OTG, download OTG app from the below link and check it
2.A USB flash storage device
This one is largely up to you. Any storage with a USB connector will work as long as it's formatted as FAT32.
How to Connect with a USB OTG cable
1. Connect a flash drive (or SD reader with card) to the full-size USB female end of the adapter.
Your USB drive plugs into the OTG cable first.
2. Connect OTG cable to your phone
Connect your USB OTG cable's microUSB end to your Android phone.
3. Swipe down from the top to show the notification drawer. No need to do this if your file manager automatically appears.
4. Tap USB Drive.
You can now browse the files on the flash drive and copy them to the phone storage. If you want to copy from the phone storage to the flash drive, follow steps 5 to 9.
5. Tap Internal Storage to view the files on your phone.
6. Find the file you'd like to share. Hold down on it to select.
7. Tap the three dots button.
8. Select Copy.
9. Navigate to your USB drive and tap Done to copy the file.
Once the transfer process completes, unplug the flash drive and connect it to your PC.