1 – You need physical server(Like PC or HP Servers or…) or virtual server (Like VmWare or ProxMox or …)
2 – You have to download and install Elastix OS https://www.elastix.org/downloads/ on your server
3 – During the installation you should add
4 – Open your browser (Like firefox) and enter the ip Address (Like : http://192.168.1.2) and then enter your user/pass you have been entered
5 – In PBX you can create user/pass for the clients by advance options
6 – Install SIP Phone (Like : Zoiper) on client systems and register it with the user/pass and ip of the Voip server (Like : 192.168.1.2)
7 – Make your call !