Hey @Magica 
I spotted your comment here about having done your first review and wanted to try help - I’ve posted it here as not to go off topic.
This handy poster covers the basics about becoming a tester.
The Great Big Review and Testing Guide has much more information in detail.
Regarding where you post the review, that would be the product page on the website of such item.
Feel free to ask any more questions and I’m sure we can help you 