Simple steps to get Inspiron 15 to boot from USB

I have an Inspiron 15 7548 running Windows 10 and have created a Rescue USB for it (in case of hard disk failure) using Paragon Hard Disk Manager. The USB is FAT-32 formatted.

So, how do I get the Dell to boot from the USB?
I have tried various settings on the boot tab of the BIOS, so far without success.

1. Should I use UEFI or Legacy?

2. Turn Secure Boot On or Off?

3. What change do I need to make to the boot order?

4. What's the significance of the Network option in the boot list?

5. Make changes just to BIOS settings (F2) or also to boot settings (F12)?

6. Mount USB drive in USB2 or USB3 port?

Help would be greatly appreciated.