string siteUrl = "https://xyz.sharepoint.com/sites/MyList/";
ClientContext clientContext = new ClientContext(siteUrl);
string username = ConfigurationManager.AppSettings["username"];
string password = ConfigurationManager.AppSettings["password"];
System.Security.SecureString passWord = new System.Security.SecureString();
foreach (char c in password.ToCharArray())
{
    passWord.AppendChar(c);
}

clientContext.Credentials = new SharePointOnlineCredentials(username, passWord);
Web oWebsite = clientContext.Web;
ListCollection collList = oWebsite.Lists;
clientContext.Load(collList);
clientContext.ExecuteQuery();