Looking at your question #3 it seems you are interested in using your second computer as a client (meaning displaying your JRiver library from your first computer. If this is the case there are a few things more that you will need to do. If on the other hand you just want a copy of JRiver on your second computer then as Jim says download and install.
If you want to use the second as a client then make your first computer your server. On the server go to tools>options>Media Network and check Use 'Media Network to share this library and enable DLNA' follow the prompts and it will give you an access key and then ask you how you want it set up i chose existing settings. Then go to Startup on the tree and then Windows startup> Run on Windows startup and check Media Server hit ok and your done with the server. On the client go to View and select Standard Mode, under playing now, right click on 'playing from Main Library'> 'add library,' give it a name, fill in access key from server and then hit ok and that will finish setting up the client. You should have access to everything on the server.