Helen,
A rough translation from Siggi Tommi’s Topo:
Drive north to Akureyri on A-1 (A as the equivilant of UK „A“-roads), continue through Akureyri on A-1 until you reach Ljosavatnsskard and then pull to your left on A-85. You drive A-85 until you reach a junction and turn again to your left on B-851 (B or even C class in the UK) drive approximately 12km. until you reach Bjorg estate where the hut/bunkhouse is, this road is probably quite bumpy and if snowy it could be impassable if you are driving a wee car.
Hope this helps.
I do hope you spend a bit of time before you start climbing to familiarise yourself to the „Icelandic Climbing Calls“, which are quite different from their British cousins (at least my experience…) ;o)
Cheerio
Halli