Which websites can I use the spoofer on?

You can use the spoofer on any site that has a queue. For example: SnipesUSA, Kicks-USA, Adidas, Yeezy Supply etc. 

Simply add the URL of the queue-it site, add proxies, and the number of instances.

From there, click create and the number of instances requested will be displayed as individual instances in essentials. You can monitor the progress of each instance by clicking the ‘eye’ located on the top right of the instance.