Unable to boot into USB

So I guess you guys can guess I'm kind of new at this, but I do have some experience with computers. Recently I installed an iso file to a USB to use as a live disk. It worked fine, but I had bigger plans. I then installed my distro onto a separate USB drive (plenty of space, distro was 8gb the USB was 16) using the drive space as though it were a partition on a hard drive.

This is where it gets tricky, the install went fine and is now on the second USB drive. However, because it has no other partitions, it has no mbr or grub bootloader. So when I try booting into it, it simply hangs on a blank screen. I can however boot into the full system, not the live edition by booting into the live USB drive I created, and selecting the second USB drive as my source. I believe this is because when I created the live USB the iso installer also installed a bootloader for me.

So my question, is what is the next step for me, in order to boot from the second USB drive without using the live USB? Do I need an mbr, a bootloader? How would I go about putting these on the USB with the full install.

I hope I described everything clearly enough, but will be glad to add any details that might be needed.

Thanks very much,
Andrew