#1 How to use it like a flash drive.
Plug it in to a modern linux. If the usb came with exfat format then will have to convert it to a common format. (pretty sure there isn't exfat in linux free just yet)
#2 To use it as a live usb.
A few choices.
One is to use some program in linux or windows to make a faux install. See www.pendrivelinux.com
or your distro's web help for ways and applications. Some distro's can boot to iso files directly. Can make it a multiboot usb.
Another is to use dd command with a hybrid-iso or a disk image of your distro choice.
Lastly is to use a modern distro and use the normal install method. Almost every distro today can use a flash drive just as if it were a regular hard drive. Might have to install default mbr while in the installer. Usually this is the best way to have linux on a flash drive. It will be able to update and keep updated this way.