In my iPhone application I have one option for import twitter followers in my friend list. (friend list which is display in my application)as per my knowledge I need to follow the steps below:
If anyone have good approach than kindly guide me.
You can use (on iOS 5 and above) the Accounts + Twitter frameworks to make your access to Twitter a lot easier. This way, you don't need to manually deal with the OAuth protocol. You can also take advantage of the fact that a user may have their Twitter account already set up at the OS level, meaning you don't need them to log in again. See links below on how to use these.
Your second question regarding followers list, you can get a list of followers using the following API Resource: https://dev.twitter.com/docs/api/1.1/get/followers/list
Using that API along with the Twitter framework should get the results you are after/
Sources
Accounts framework reference: http://developer.apple.com/library/ios/#documentation/Accounts/Reference/AccountsFrameworkRef/_index.html#//apple_ref/doc/uid/TP40011024
Twitter framework reference: http://developer.apple.com/library/ios/#documentation/Twitter/Reference/TwitterFrameworkReference/_index.html#//apple_ref/doc/uid/TP40011014
Sample code on how to use these frameworks: http://developer.apple.com/library/ios/#samplecode/Tweeting/Introduction/Intro.html#//apple_ref/doc/uid/DTS40011191