How do you make a welcome page?
 

I want my site to have a welcome page with a similar layout to this one:

www.reefcentral.com

Where you can have a picture of the month at the beggining and a menu to the left.

My current site is looking like this: http://www.acuarios.com.mx/foro/ I like the layout but I would like to have first the welcome page I previously described. Any ideas on how to do it?