If you already have access token value and secret, you can do something like that:
ITwitter twitter = new TwitterTemplate("consumerKey", "consumerSecret", "accessTokenValue", "accessTokenSecret");
// twitterApi.UserOperations.GetUserProfile();
that is equivalent to :
TwitterServiceProvider serviceProvider = new TwitterServiceProvider("consumerKey", "consumerSecret");
ITwitter twitterApi = serviceProvider.GetApi("accessTokenValue", "accessTokenSecret");
// twitterApi.UserOperations.GetUserProfile();
How do you get the access token secret and value?