I am setting up an api key and it looks like I do that on the Mashery site. My question is, do I have to create my mashery account with the same login credentials that I use for my constant contact account? If I use different credentials, how does mashery know where I will use the api keys to access my CC account?
The developer accounts created with Mashery are completely separate from your Constant Contact account, and you can use any credentials to create it. The way that we link your API keys back to your Constant Contact account is using the Access Tokens that can be created once you have an API Key. One easy way to think about it is that the API Key represents an application or integration. The Access Token represents permission for a specific API Key to access a specific Constant Contact account, and is unique for every combination of API Key and Constant Contact account. Thus, when you have both, you can successfully connect to and access the desired Constant Contact account.
Hopefully this helps to clarify, and please let us know if you have any additional questions!