How do I put my wpmu dev details into the wpmu dev dashboard plugin?

I've installed it on a newly created Wordpress MS and network activated it but when I go to the plugin page at wp-admin/network/admin.php?page=wpmudev I see the form saying "Get your free API key" that'll let me create a new account but the click here link after "Already a member?" takes me back to the same page - wp-admin/network/admin.php?page=wpmudev

It seems all I can do is create a new account here. But I already have an account and just want to enter my API key but can't find where to do that.