Yes it is always difficult with newer computers / laptops that they have no serial port.

And for a good and reliable success you need a computer / laptop with a real comport and wxp system.
Many have already gone in the failure by trying it with a USB to serial cable and W7.
I myself always use an old laptop with a real serial port and Windows XP for these jobs.

Regarding the adapter .., it is also easy to make, even without the board, a direct cable.
You need two DB9 female connectors where the computer side pin 2 goes to the box pin 6.
And computer side pin 3 to the box pin 4.
And the computer side pin 5 (gnd) to pin 5 of the box.

For more on this, see this drawing.