iOS twitter integration using OAuth like in Instagram


I am implementing login with twitter for my application. I want to allow user to login from settings and if settings account is not configured, then login with Custom view instead of webview. I want to create same functionality as Instagram have implemented. I have implemented the login with webview feature but we want custom UI for login. Do I have to request some special permissions from twitter to do that.
Kindly help me to solve the problem.