I have no idea if the tablet can be booted from the microSD or not. Using a FAT32 formatted USB stick the label should be USB. Just unzip the files to the root same as you did with the microSD already (or copy them from the microSD, should make no difference).

You also need a (powered) USB hub and USB keyboard&mouse.
Just press ESC while booting, select Boot Manager (here you need the mouse) and finally select the USB stick (with the keyboard, if I recall correctly).

Skim/read through this Onda thread, all the information you need should be mentioned along the way.