You can't use a theme from outside WordPress.com on a WordPress.com blog. You can use it on a paid Godaddy WordPress blog.
You can blog here for free, but you say you've purchased upgrades to customize the look. That still will not enable you to use an external theme on a blog here: there is no upgrade that will allow that.
You need to choose which you would rather have: that theme, or hosting at WordPress.com. If you go with Godaddy and the theme you have downloaded, you need to ask for a refund for your custom upgrades here. Do that from your Upgrades page, immediately.