In Joplinportable,How to insert a local picture in a .md file?

I want to know how to insert a local picture in a .md file? I use the JoplinPortable in a USB. but can't insert a picture at the another directory in the USB.

As far as I remember (I have no portable system around at present, but I was used to use it some time ago)) it works like the desktop version. There is no manual copying of files needed nor helpful,