If you can boot any linux on the machine, follow instructions in Fixing Lilo with uefi system and no optical drive (obviously you'll need to adjust it for different bootloader).
To transfer the image to a Flash USB drive directly, you can use
dd if=/path/to/your.iso of=/dev/sdX bs=8M
/dev/sdX is the kernel device of your USB drive. This of course destroys any data*) previously on the USB (but any method does that anyway). As a side note, the verb "burn" is usually used only when the target media is written to with a laser (e.g. all the variants of CD/DVD/BD), which flash is not.
See also this guide on Fedoraproject.
*) strictly speaking, in the case of a flash memory based device it doesn't really neither destroy nor all the data - due to wear leveling, the blocks are realocated, so some of the previous content will stay untouched and also only the beginning of the device will be erased (writing 3GB image on 8GB flash doesn't alter the last 5GB).