1. Determine what kind of advertisement you are going to add to the page. If you are using an advertisement from an ad network, they should provide you with the code you must add to your pages. If you are selling an ad space on your own, then you must create the code yourself.
2. Determine where you are going to insert the advertisement code. Look on your Web page and find the best spot to insert the advertisement.
3. Find the spot you are going to place the advertisement in your Web pages source code. If you are using a WYSIWYG Web editor (such as Dreamweaver or NVU), open your Web page in the editor. Click on the button that says 'Source' or 'Source Code.' If you code your pages by hand, then open the file in Notepad.
4. Scroll through the lines of code to find the spot you selected for your advertisement. The code is written in the order that it appears on the page.
5. Copy and paste the code into the editor or Notepad. Unless you are adding the code to a CSS style sheet; you must repeat this for every page you want the advertisement to show up on.
6. Save the file, and preview it to ensure that you placed the advertisement code in the proper spot.