(a) Create a new VLAN under FortiGate > FortiSwitch VLANs > Create New. This will automatically create a new VLAN sub interface under root-sw Switch Interface.By default, Switch Port13 belongs to vsw.root-sw VLAN. Now assign VLAN50 to Port13 (right click on vsw.root-sw and select VLAN50) on the newly added switch and connect to the workstation. The workstation will get the DHCP address from the FortiGate's VLAN50 interface DHCP range under root-sw interface. Many VLANs can be created under FortiGate > FortiSwitch VLANs and VLANs can be assigned to either Switch Ports under FortiGate > FortiSwitch Ports.
(b) Enable DHCP and assign a range. Administrative Access (https, ping etc.) can also be enabled.