There are a couple of options to check your Voice Mail on your softphone application.
1. Pressing *97 on your dialer then pressing call or send you can access your voicemail
2. Pressing the "VM or VoiceMail" softkey on your softphone app will take you to your voicemail, however you may have to setup your caller ID or *97 process within the account settings.
In either case, one or the other methods may be used to access, setup and manage your voicemail as well as your greetings and message options.