I have a SF300 series switch.  I need to enable DHCP.  When I attempt to enable it, I get an error message to disconnect all DHCP clients.  How do I do that??????

I am very new switch configs.  I need to know what steps I have to take to enable the DHCP Server on a SF300 series switch????  I keep getting errors to disconnect all DHCP clients, but don't know how or where to go.