Unfortunately, there is not a way to use the DirecTV's wifi capabilities with the Slingbox.
I assume you are trying to run video from your Slingbox to your DirecTV. I can't quite tell, but it sounds like you're running into the issue of your DirecTV box having only HDMI for its video output, and you needing component (red, blue, green, red, white) or composite (yellow, red, white) cables in order to hook it up to your Slingbox. If this is the case, you have a couple options.
1) Most DirecTV boxes that have HDMI only also have a 10-pin port on the back that is intended for hooking up to devices that don't have an HDMI input (like your Slingbox). If your DirecTV box has a 10-pin port, you should be able to acquire a 10-pin to component cable from DirecTV.
2) If you do not have the above option, you can always consider an HDMI adapter, which allows you to convert an HDMI signal to a component signal. You can find information on this here:
Hope this helps! Let me know if I'm totally off base with the issue you're experiencing!