I’m also new in Picard, but you can choose the green “Tagger” Button to get the release into Picard. If the green “Tagger” Button isn’t shown, you have to push “Look in Browser” in Picard one time per browser session (the reason is, that the musicbrainz website needs the Http GET Parameter to realise, that you are a Picard User who wants the “Tagger”-Button)
But you also can drag and drop the release URL into Picard.
So you can immediatly get the release if you dont need to use the “Lookup” search. If you edit this release, that is no problem.