MicroSIP is a free Windows softphone with numerous features. It can be downloaded from the official MicroSIP source, Softpedia, SourceForge or Portable Apps.
To add a new account, click the drop down menu in the top right corner (aka the Accounts menu) or right click the blue phone tray icon and then click "Add Account...".
At a minimum, you want to complete the following fields:
Account Name: how your account will show in the list of accounts, e.g., EZvoip 1
Username*: what we sent you as YourUserID in your Welcome Email
Domain*: the recommended domain from the Welcome Email or our list of servers
Password*: the password we sent as YourPassword in the Welcome Email.
Optionally, you might want to enter a Display Name for outgoing Caller ID and *97 in Voicemail Number if you have it configured.
We will soon have a more detailed guide for installation.