I've been trying to install Ubuntu alongside Windows 10 64 bit. I've burnt the iso image into a USB stick (with Rufus) and disabled fast boot and secure boot and changed the boot order but when I restart the computer it still boots to Win10. What should I do now so that I can boot the USB.
You didn't indicate what machine you're using. On some machines, within the BIOS, there are two places to change boot order. Make sure all of those settings are correct.
Also, if you have more than one USP port, you cant try a different one.