Fresh Multisite instal - Can't log in with my existing api key

Hi,

I did a fresh Multisite instal and would like to continue to use the wp mu dev dashboard- plugin with it. Where do I insert my existing api key or do I have to register a new one? I can only find the place to register a new one...
Quick assistance would be appreciated 'cause my monthly membership is about to expire (I'm still considering continuing the membership though.. )
Thanks!