There are regular flights to Donegal airport from Dublin – www.donegalairport.ie In addition, City of Derry airport, www.cityofderryairport.com offer scheduled flights from London Stansted, Manchester and Glasgow. Transport can be arranged to Ramelton through the contact details.
Bus Eireann have usually 4 buses from Dublin to Letterkenny. Letterkenny is just 7 miles away and the route is served by taxis and the Lough Swilly Bus Company. Letterkenny is also well served from Derry bus Lough Swilly. There is a regular express service (1.5 hours approx) from Belfast to Derry with Ulsterbus. The train also serves Derry from Belfast.
Whether you travel from Derry, Lifford (eg from Dublin), or Ballybofey, you will come to a dual carriageway into Letterkenny. There is a large roundabout before reaching the centre of the town (at the large stone-clad Tourist Office). Turn onto Route 245 here (it is signposted for Ramelton, Milford, Downings, etc). After 6 miles you come to Ramelton.