Give this document a look...
https://support.dell.com/support/edocs/network/PC35xx/en/UG/HTML/ryanugck.htm#wp1392930There are global commands for enabling the voice vlan, as well as a port specific command.
Global:
voice vlan enable
voice vlan id <vlan id>
Then on the ports:
voice vlan secure
There is also a show voice vlan command to view the ports it is enabled on.
Hope this helps!