Here's a quick way, assuming you have already installed Avisynth.
Open Notepad (or some other text file editor on your PC.)
The most simple script would be -
DirectShowSource ("Drive:\Path\Yourvideofile.mpg")
Note: You need the quote marks around the file path.
Save the file as Yourvideo.avs
Now open Wax and use the Add media button, choose the .avs file and it
should load the video and audio.