To install FoxyShop, follow along with the steps below. There are three important things to do in order to get your installation up and running smoothly. Everything else is optional. In your WordPress admin, go to the Products / Manage Settings menu and check these things:
First Important Thing! You must put the automatically generated API key into your FoxyCart settings (click here for the advanced menu in the FoxyCart admin). Enter this code on the FoxyCart site in the “store secret” box and check the box that says “would you like to enable cart validation?”. This ensures that no link tampering can take place on your product pages. If you don’t enter this code on your FoxyCart account, nothing will happen when you try to add products to the cart.
Second Important Thing! Check your jQuery settings. If you are already using jQuery on your site, you may uncheck the jQuery include option in the FoxyShop settings so you don’t get two competing versions which causes problems. By default, FoxyShop uses the latest version of jQuery.
Third Important Thing! Check your permalinks. For best results, set your permalinks to Month and Name or Day and Name and click Save to flush your rewrite settings. If your product pages aren’t showing up, flush your rewrite settings again. If your product pages appear unstyled, you might be using a WordPress framework that bypasses header.php and footer.php. See the FAQ for suggestions or use a shortcode.
There are a lot more settings on this page that you can review, but those are the critical ones.
I recommend that you use the latest FoxyCart version and set the password hashing to phpass.
If you want to enable custom file uploading, make sure that the /wp-content/uploads/ folder is writable or at least that there is a writable folder underneath it called customuploads.