Not sure what info you are looking for, but typically people would navigate to the applicable sub community from the home page here: https://community.sling.com/welcome
You can also search for the topic you are looking for, and often a discussion will already exist.
If you are not seeing or able to respond, make sure you have your first and last name populated in your user profile. This is required to respond to discussions.
This page also has an FAQ section about out community: http://support.slingbox.com/sitecore/content/Support/KB/KB-8004