Fortiswitch Standalone Voice Vlan Configuration

Hello everyone,

I need some help, i have a Fortiswitch 148F-FPOE, Fortivoice 300e-t, Fortifones 480B and Fortigate 60e. Fortiswitch working as standalone. I have two vlans, one for data (VLAN10) and one for voice(VLAN20). I want to connect PCs to fortifones and PCs can lease an ip from data vlan and fortifones can lease an ip address from voice vlan automatically. 

How can i configure the switch ports to achieve that? 

Thank you