FortiWiFi 60D - How to access from LAN traffic to the WiFi traffic ?

If both LAN and WIFI are merged into a single switch interface then wifi users should be able to communicate with LAN devices unless client isolation is enabled on the wifi SSID.  (Guessing this part, though.)

If the LAN and WIFI interfaces are separate from each other then you will need to set up two firewall policies - each going in the opposite direction with NAT disabled.