Facebook writing on users wall

I have an ios game app. I want a facebook app such that once the users accepts my app to write on there walls, My app should be able to post on their walls. Like : appstore once accepts can write on the users walls about the new apps. Typically these are the things i wan to post. : Welcome message ( once) : Daily winners in the contest.( daily) : any changes in the terms ( very rearly) I have the web site with SSL ready, and the face book appid. I need the ability to know who all the users accepted to write on there walls.