Accessing API Key for trello OAuth 1.0

[Merge]

I'm trying to implement OAuth 1.0 and it says that I can access my API key by logging into Trello and visiting https://trello.com/app-key/. However, even though I am logged in, the url returns a 401 error. How can I access my API Key? 

[Harry watson]

Hey! Trello's API interface utilizes token-based validation to allow outsider applications admittance to access to the Trello API. When a Trello client has conceded an application admittance to their Trello record and information, the application is given a symbolic that can be utilized to make solicitations to the Trello Programming interface for the client.