The island of Crete has two significant airports, Nikos Kazantzakis airport at Heraklion (Greek website here) and Daskalogiannis airport at Chania CHQ (Greek website here) that serve international and national flights. A third and smaller one is located at eastern side of Crete at Sitia.By sea
The transportation from Chania and Heraklion to Rethymno can be done either by taxi, or by bus which is more economic. There are two bus companies that serve the transportation to Rethymno the one located in Chania KTEL Public bus service Chania - Rethymnon and the other in Heraklion KTEL Heraklion-Lasithi S.A.
The IMS is located in the old town of Rethymno. For specific directions please see map above or Google directly.
Where to stay while in Rethymno
Recommendations for accommodation can be found here.