If you want the products in your CafePress Shop to show up in the Marketplace (public forum, including iGive), you will need to edit the CafePress Shop account settings to make your products available in the "marketplace".
If you need help doing so, you can call the CafePress shopkeeper help line at (888)800-4359 x1 and they can walk you through it.
Once all your products are available in the Marketplace, be sure that they are properly "tagged" so that they appear in the search results. The CafePress search box hits on "tags" as opposed to the product title, so you will need to "tag" all the items with your cause name to ensure shoppers can easily find them. This is also something the shopkeeper help line should be able to assist with. When a shopper buys from your CafePress shop through iGive, you receive the donation listed on iGive (currently 8.0% of the purchase) AND a different rate of commission directly through Cafe Press. Our contact indicates that the direct payment would be lower when combined with the iGive payout, but there would still be a direct commission earned. It may take some testing to determine which will be the highest total payout for your Cause and where you should direct your supporters to make the most of both your CafePress & iGive partnerships.