I assume you have already done a proper Forum Search for your model number in case other people have already answered your question ?
If so and that didn't help then check out this thread: https://community.sling.com/thread/3300?tstart=0 (Ignore the part that says the 500 does not allow Custom Remotes. It does now. I have asked the moderators to change that thread but so far they haven't done it )
Come back if it that doesn't help either.