Problem calling in with asterisk

hi all?
I have so far configured my asterisk with relative success. at least on can call in and out easily in the lan. Now here is my issue:
how do i get to call into the voip box from say my cellphone?
here is how things are set up:

  1. Our voip provider is our ISP and the number we have been given is +1 4154490205
  2. I have 6 phones in the office.

do i need to connect one rj45 connector to the WAN port of the phone? and the rest of the phones to the switch (these are the ones with extensions, so when one calls the main line it can route the calls to the others)