Pppoe static ip configuration

Hi,
We are using broadband connection and configure pppoe in D-Link ADSL modem . I connected dlink lan port with sonicwall wan interface and enable DHCP in that port. Now I need to access my sonicwall from outside. We brought static ip from ISP. But I don't know how to access this ip address in firewall. When I enable DHCP in wan interface sonicwall takes dlink lan ip address as its wan ip address. So can anyone help me how to assign static ip address to access device from internet