Ijoomla v3-0 on Wamp 2.0

The problem is: I want assign a specific module (banner) on specific issue, article, etc.
This was working find with the hold version of Ijoomla (with external link inside the main menu), but now I dont find any solution to affect module (banner) on certain page of my website.

I read the Show Modules on Article Page instruction, but the instruction "in order for this functionality to work you will need to modify your site template file   "Open your template file and look for the following lines:..?>... <meta http-equiv="Content-Type" content="text/html; <?php echo _ISO; ?>" /> " is not clear for me, I dont find this template file ?!, its hard to find the way.. I create all the possible link inside the main menu, I use template elemental.. I know this is a easy question .. can you explain this step by step. Best regards. Patrik