Two things. Well, three.
Firstly, please avoid sites that are offering "Premium resources" for free. That site is basically redistributing pirated software. That would be against the Cloud services agreement as it is, and customers found to be breaching those terms could have their subscription cancelled. This is very important but also worth noting that some sites modify code to be malicious in nature.
Second:
It's unlikely the add-on will be compatible with XenForo Cloud (which runs XenForo 2.2).
Thirdly, you don't even need an add-on for this. XenForo supports Q&A forums/threads out of the box.