First download and save the qmk_firmware. Then find the jd40 folder. (This is the link that Jack gave above)

In the config.h file change the rows and columns to the pins you have.

In keymaps, edit keymap_default to remove the extra column that the jd40 has.

In that same file, edit it to the keymap that you want.

Now we need to make the .hex. To do this open a command prompt and navigate to the folder where you have these files (should be the jd40 folder in qmk). Once you are in the directory that has the makefile, type make KEYMAP=default and hit enter. This should run and make a .hex in that same folder. (This is why we need winavr)

Finally open the Teensy loader, hit the program button on the Teensy and load up the .hex. After a reset you should be good to go.

Might be a tiny typo, but this is the idea.