I assume you are referring to http://askubuntu.com/q/671744/85695. First of all, you only asked this yesterday! Have a little patience :)

Then, it is hard to understand what you mean:

> My usb drive gets mounted under /media/username but i tried using umount to mount under /media/usbdisk

You can't use `umount` to mount something, only to unmount it. What is the actual command you ran?

>when I used multisystem multiboot usb creator it doesn't recognize my usb under /media 

You used it to do what? How does it not recognize it? Was there an error? Could you add a screenshot showing it? In any case, it probably looks for the default locataion, why did you change it?

Basically, please edit your question, explain exactly what you tried and exactly how it failed including any error messages. Ideally, add the information I asked for here, including a screenshot showing the problem. 

In general, questions that are hard to understand don't get answered because people just move on to the next one. To increase your chances of getting an answer, you should always try and make your question as clear and as detailed as possible.