How to create an account:
Click on the [REGISTRARSE] button in the upper toolbar.
On the next screen, type your desired username in the upper textbox.
Type your email address in the next textbox, an check the checkbox if you want to keep this email hidden from other users.
Type your password in the textbox below that, and again in the next textbox to verify it.
At the bottom of the screen, check the 'Acepto' textbox to accept the terms of use, and hit the [Registrarse] button to register.

How to log in at the forum:
Click on the [INGRESAR] button in the upper toolbar.
On the next screen, type your username in the 'Usuario' textbox and your password in the 'Contraseña' textbox.
You may specify a session length in minutes in the textbox below password, or check the checkbox to always remember your username/password.
Hit the [Ingresar] button to log in.

How to change the forum language to English:
Log in at the forum.
Click on the [PERFIL] button in the upper toolbar.
Click on 'Configuración de la cuenta' in the left-hand menu of the profile screen. (Just below Editar Perfil)
Change 'Idioma que deseas usar' from Spanish to English.
Enter your password in the textbox next to 'Contraseña actual'.
Click on the [Cambiar perfil] button.