In order to use it in SDL Trados Studio you need to have an active Subscription that contains integration with SDL Trados Studio. See this article: https://languagecloudsdl.uservoice.com/knowledgebase/articles/835812-what-type-of-subscriptions-are-there-available-for
Once you have a subscription with SDL Trados Studio integration you can use SDL Language Cloud in Studio.
In Project Settings go to Translation Memory and Automated Translation and Add SDL Language Cloud:
You can get this log in screen: