Call From Other On Internet

I have asterisk v 1.2.7 and i create local connection my server ip was and the range of my ip is
i have one static ip and that directy connect to one router with x ip then this router create ip with range and that connect with ip to my proxy server then i can use internet and show my web page and else.
now i want use asterisk from internet to my local server
how can i do?