When you install Affiliate via WordPress’ Plugin menu, you may see the following error message:
This means your upload size limit is lower than our plugin’s file size. You can check your file size limit easily at http://www.yoursite.com/wp-admin/media-new.php . You’ll see “Maximum upload file size” information on that page.
You can contact your hosting company to increase the upload limit for you.
Alternatively, you can extract the plugin file and upload it to /wp-content/plugins/ menu via FTP.