Review the 5 videos in the museum, and Mews will appear to give you further instructions.
You find him in the lab, where you first talked to him. From the helipad. it is just to the left.
Harold Mews is real only on Poptropica's Cryptids Island.
The Cryptids Museum is on the first floor of the Mews mansion, to the right.
You have to look at the 5 videos in the museum and then Mews will show up. (You only have to open each one, not look at the whole thing.)
When you come downstairs in the Mews mansion, and enter the museum at the right, your character will suggest watching the 5 videos on the cryptids. So you have to do that before Mews will appear again.
He should appear in the museum or the lab (to the left) after you have watched all of the videos in the museum.
The heliport at Mews' house is out the door, then to your right. You cannot use the helicopter until you have reviewed all of the videos on cryptids and spoken to Mews.
He appears only after you have watched all of the videos in the room (you don't have to watch them all the way through).
It is one of the locations on the helicopter GPS system on Cryptids Island. Once you are rescued by Mews, review the videos and you can go in search of the four cryptids.
After Mews leaves your room, drink the water and go downstairs, to the museum on the first floor (right). Watch the 5 videos and then Mews will arrive and you can begin hunting for the cryptids in his helicopter.
You awake in the Mews mansion. After he leaves, drink the water, go downstairs, and enter the museum (first floor right). Review all 5 of the cryptids videos and then Mews will join you.