Contacts Syncronization options opn ANDROID Phone from my server to phone

Hi! I am developing an android application that picks up contacts from the phone book of a user to my server. I am able to pickup contacts from the phone book on mobile to the phone book on my server in a user account. Now i need a solution so that i can pickup contacts from the phone book on my server to the phone book on mobile.
1) What are the steps to ADD ACCOUNT in Settings of an android phone if a user installs my application.
2) How can i retrieve phone book contacts on my server of a user to his android phone book on successful login in my application.