AuthCallback.cs

private void AuthCallback(ILoginResult result)
{
    if (FB.IsLoggedIn)
    {
        // AccessToken class will have session details
        var aToken = AccessToken.CurrentAccessToken;
        // Print current access token's User ID
        Debug.Log(aToken.UserId);
        // Print current access token's granted permissions
        foreach (string perm in aToken.Permissions)
        {
            Debug.Log(perm);
        }
    }
    else
    {
        Debug.Log("User cancelled login");
    }
}