FortiSwitch 224D-FPOE Question

Please help I'm losing it. On my dell switches I insert an internal IP and plug network cable into any port and I can ping, connect or other wise have a functioning switch. Can connect other devices to it and they have network access. My fortinet has a mgmt port and an internal interface. If I assign the internal interface with a static address on my network and try to ping I get nothing. If I assign the mgmt address an internal IP and connect it to a cable that has access to network than I can ping the fortigate and see it on the network, but just with the cable in the mgmt port and plugging in a laptop it does not have network access. It seems I have to plug another live wire into the a port to make switch active. I tried leaving the mgmt port alone and setting internal IP and plugging in a wire for network access and the laptop worked but could not manage the switch even though those options where on. Most of the switchs I have work with did not have the mgmt port so assigning an ip to the switch and plugging in a cable seemed the very least you had to do to get it on the network. What is the proper way with Fortinet what am I doing wrong.