I don't think the API needs to be put anywhere, at least in case of easydiscuss...
API is generally needed for network install, or for updating( in this case you just need to download latest version and install it over previous installation.. )
Still would like to see what the support has to say...

Hey Ayhan,

Thanks for purchased Easydiscuss product recently

Yes, currently you no need insert your API key into Easydiscuss configuration settings is because that feature haven't implement in Easydiscuss yet.

Thanks for sharing Akashlal