Setting up first VLAN

I am looking to split my network into several smaller vlans. I have never used vlans fully before however I understand the concept and the terminology.

So here goes - my setup includes, 5 dell 3448p switches. (can only stack 4 so they are all in standalone mode).

These 5 switches plug into a Netgear Prosafe GS724T which then plugs into a SonicWALL NSA2600.

I am using port 3 on 1 switch to test at the moment.

On my 3 devices I have created 2 VLANs,  Phones VLANID:2 and PCs VLANID:4

On my SonicWALL I have added the VLANs to interface 0 which is where the netgear plugs in to and everything currently talks on a normal subnet.

On the 3448p I have set up the port as "General" with a PVID of 2, under the VLAN membership settings I have 2 as untagged and 4 as tagged.

Now i think i am heading in the right direction here, however i don't know what to change on my netgear. As all the ports from the 3448p will be forwarded through it, and i don't want to kick all the computers on that switch off the network fiddling around with it.

I will also have a VLAN with an ID of 5 which other ports from the same switch could use.

any suggestions or feedback is appreciated.