OK, it looks like it has a single Ethernet phy from the photos.
So, for each VLAN you want to use, create an interface with that VLAN on the "active" phy (the one that shows link up). Then bridge the virtual AP ("SSID") to the interface you want. If you want to isolate the VLANs, you'll need firewall rules preventing at least forwarding between them, as well as deciding if you want either of the VLANs to be able to access the router's own IP addresses.
For example, here's a VLAN interface, the way I uses them for trunking VLANs
config interface 'vlan883'
option type 'bridge'
option stp '1'
option ifname 'eth0.883'
option proto 'none'
option auto '1'
option delegate '0'
Then, in /etc/config/wireless
, I set the network
for the wifi-iface
to vlan883
Note that it is eth0.883
that sets the VLAN ID, not the name of the interface!