You can reach Tripiti via car or bus from Thessaloniki

Car directions from Thessaloniki airport https://goo.gl/maps/pzchvFLsWn...

Bus station location and time tables (https://goo.gl/maps/nUFgXgpgu5...) (http://www.visitammouliani.com...) 

Take the ferry from Trypiti port to Ammouliani island (ferry schedule) 

It takes 12minutes to get to the island and then 2 minutes to Villa Chara.