Hi Jose
To add a right side bar you go to admin > appearance > Atahualpa Theme Options > Sidebars and Widgets > style and configure SIDEBARS.
Scroll down to RIGHT Sidebar: display on and tick the box beside "page" pages
This will now mean that the right sidebar will be on all pages, which you don't want.
Go to RIGHT sidebar: Don't display on Pages: (directly underneath and find the id of each page which isn't the poster page, it explains how to do this on the right.
To alter the width of your sidebar go a bit further down the page. It is going to have to be very narrow on this page because of the width of allposters.
Once your sidebar is in place you can then go back to the main admin (not Atahualpa) and choose Appearance > Widgets. Click on the arrowed box on the right entitled Right side bar and drag 'PHP code' into it.
You will then be able to paste any banner code within that box.
Hope that helps…I am planning on doing some instructional videos for all this type of stuff when I get a spare minute
Penny