Ext3 is native Linux, i did it via my pc, using partition manager, but i think you can do it on the box,
Epg setup/ Blue/ red, global settings, leave them as is, but change path to media/usb, then save. Scroll to Rytec UK or Satmate UK, thenprovider settings, settings, enable refresh, to yes, set time, save. Download now, that's it mate, it looks more than it is, it's easy to setup.
To mount the USB stick, blue, blue, devices manager, mountpoints, scroll to media/usb, save, reboot. you can also format in there but i have never used the format option but it should be ok. It's all quite easy when you see it, you shouldn't have to much trouble.