First of all, let me tell you that affiliate ads are quite different as compared to google ads. In google ads, the objective is only to get a click from visitor. But in affiliate ads, we only get some earning when the visitor not only clicks but also purchases the product. So, every act while working on affiliates must be based on the concept to encourage a buyer to buy and to convert a visitor to buyer. Here are some more points to consider.
Do highly targetted work
Let me clear one more thing. Right now, we do not expect you to place affiliate ads on each and every page of your website. Its better to target only on those pages at first which atleast have some traffic of visitors daily, which act as entry points to the visitors from search engines etc.
How to select the target pages
Look at the admin->logs->keywords section of your website. You can see that which pages of your site are optimized against which keyword in which search engine. Just make the pairs of keyword and respective page in an excell file. These are your targetted pages. Also include the homepage in your list. Normally, the homepage gets maximum visitor traffic so its very creative to select and place your best ad on the homepage at right place.
First steps to write your ads
By now, you know the web pages urls on which you have to write (or optimize) the ad. First step is to select the most appropriate affiliate. I assume that now you already know most of the affiliates and their products from the provided excell files in the last month. If you can't find the proper affiliate, use other networks such as linkshare, CJ (their login information has already been passed to you).
The ad can be of any format that you like. Its not a good idea to place only the affiliate link as an ad. You should add product desription, salient features or anything that switches the visitor to buy. You already know that the visitor has come through the page by typing which keyphrase in the search engine. This would also help you in writing the ad. If there is a need to modify your article for the ad, you can do it. You can also capture the image from affiliate website and place it in your ad (if appropriate). In other words the objective (to initiate a purchase from our ad link) is important; the way how to achieve it can be anything.
Note: This is a part of your job for the month of July to work on affiliates on all the targetted areas of your website. If you need help anywhere, letme know.