You might need to do a bit of research on the Wiki FAQ
http://wiki.jriver.com/index.php/Category:Frequently_Asked_Questions, for example the Media Network topic.
For seeing and browsing your MC library on an iPad, you've probably got four choices:
1. Use WebGizmo, which is a browser-based remote control for MC and included with it, details are in the Wiki.
2. Buy the JRemote app, which is a third party native iOS remote control app, not created by JRiver (see its dedicated thread on the third Party board
http://yabb.jriver.com/interact/index.php?topic=79104.0)
3. Use a remote-desktop product to access MC directly from the iPad, e.g. Splashtop.
4. Enable MC's DLNA server and use a UPnP/DLNA controller app on the iPad.
For sending music to your hi-fi, here are some options.
1. Use a remote control app or DLNA controller app such as the ones mentioned above, use them to play music on the PC, and hook-up your PC's audio output to the hi-fi, or
2. Use them to stream to the iPad and hook up your iPad to the hi-fi, or
3. Use them to stream to the iPad and use Airplay to send to the hi-fi, if your hi-fi is Airplay
4. Use them to send music directly to the hi-fi from the MC PC, bypassing the iPad, if your hi-fi is a DLNA renderer (which will appear as a play-to zone in MC).