You can fly to the international airports of Athens or Thessaloniki , then take a coach to Volos, and from Volos take a local coach (or taxi) to Horto.
During the summer months (mid-May - mid-October) you can also fly direct to Nea Anchialos airport just outside Volos where you will be transferred into Volos by bus and from Volos take a local coach (or taxi) to Horto.
Athens - Horto is 357 km / Thessaloniki - Horto is 290 km
Alternatively, you can fly to the nearby island of Skiathos, and travel by ferry from Skiathos to Volos, Platania or Katigiorgis and then on to Horto.
Coach (KTEL) connections from Athens / Thessaloniki to Volos: www.ktelvolou.gr
Thessaloniki - Volos: 2.5 hours (20.20€)
Athens - Volos: 4 hours (30€)
Volos coach station (KTEL): tel. +30-24210-33253
Volos taxi service: tel. +30-24210-52222
You can take the ferry from Venice, Ancona or Bari (Italy) to either Igoumenitsa or Patra.
The routes to Horto are very picturesque.