What I'm getting from yout post, is that you would like to know how to connect the Slingbox using HDMI cable.
Please note that at this point the HDMI connection is not compatible with the Slingbox.
You can check the following about that type of connection when using the Slingbox.
Well maybe the question is how to convert from HDMI to composite RCA connectors. I found two options online, one using a powered converter box for almost $70 and another which looks like it is just a cable with HDMI on the one side and 5 RCA connectors on the other side for about $10
Will both options work?