First you need to clear your concepts , what is FXO and what is FXS .
Second lan card and and FXO card , both are two different things .
Use Soft phone ( eyebeam or bria ) as a phone on your system and digium card as a FXO .
Reading Asterisk guide will not help you if you don't know whats the difference between FXO and FXS .
Here is some conceptual thing , may be it will help .
FXO ------ connect phone line ( example PTCL )
FXS ------ connect your phone ( your home telephone )
Your can use IP phone or Soft phone , so you don't need any FXO port .
Wish you all the best .
M Asad Rasheed