Create widget areas in wordpress theme

Hi, can anyone help me how to add more than one area for any theme wordpress widget?
I have several themes wordpress, but I want to add at least 2 widget areas to place.
I followed the instruction in this guide: http://www.jose-aguilar.com/blog/crear-zona-de-widgets-para-anadir-plugins/, but I only used to add an area, if I add another I fails.
I welcome your comments and help. Thank you.