You go to moviestarplanet2.com, where you are presented with two avatars.
If you already have created a user or want to log in with your MovieStarPlanet / BlockStarPlanet user, you click the Log in link that is located on the bottom right-hand side in the character selection screen.
You will now be asked to enter your username and your password.
Welcome to MovieStarPlanet 2!
If you haven’t created a user, here is an article on how to create one.