I have Ubuntu on a USB drive, each time i boot it it is a clean installation, i.e. there is no persistent files. I would like to be able to boot it up, and access a couple f files from the USB... as in have files already in the Ubuntu system? Is there anyway of adding them to installation files on the USB?
You need to create a Presistent USB to be able to do so. To create a presistent USB you can use the universal USB installer.
Once you run the program, you can set the amount of space that you want to accomplish your task. You can do that under Step 4 in the program. See image below.