How to get api key: Login to your mailchimp, go to account(top right corner). Click Extras -> Api keys. You will see list of api keys created before, use one of them or create one.
How to get list id key: Login to mailchimp, click list menu from the top menu bar, click any list created(create one if you don’t have). Click Setting -> List Name and Defaults. Check there is a key in right corner of that.