Using different SDL Language Cloud accounts

I have setup a free SDL Language Cloud account. If I navigate to File>Language Cloud in Studio 2017 or add Language Cloud Machine Translation to a project, I see that I am automatically connected to my free account and can use the service immediately.

But, if I receive an API key from a company so that I can use the company’s Language Cloud trained engines for a specific project, I see no way to of doing so. How do enter an API key from another account, If I already have my own Language Cloud account?