Student needing help PLEASE :(

Hey guys, im very new to VoIP and PBXs. I want to make a simple network that has a softphone talking to another softphone with Asterisk. the network is very simply, i inserted a image :smile:

Im just having trouble installing Asterisk and im not sure how to make it connect or work so the phones will talk? And how would i go about testing the network for QoS ( jitter, delays and voice quality). Also for redundancy how could i implement a second PBX to take over if Asterisk fails? Im hoping to use this information in the future!

Please Help guys, any and all help would be appreciated!