Thanks for the explanation,Sven.
Sorry if I do not understand.
Pins 2 and 6 are those of the PIC 18?
No, of J3. You asked how to set J3 so I gave you the pin numbers of the respective J3 pins as outlined in the schematic.
Function of LOAD HxCFloppyEmulator asks me a file image, which I have to upload?
Just load any image the emulator supports (see project homepage). Use any disk imager software you want, e.g. IMD (supports almost any disk format) or Winimage if you don't need support for non-PC compatible disk types. Once you have created the image(s) you can export it into a *.hfe file, you can then mount the hfe file on your SD card emulator.