There are two proper ways of addressing me: The informal way (much preferred by myself) is "Einar" (since that's my only name). If you feel obliged to be formal (for example, if you represent the Queen and have a message for me), you need, of course, to use the highest appropriate title. That happens to be "His Royal Highness", as witnessed by the following genealogy:

Ingjaldur (the White) Helgason (King in Ireland)
Ólafur (the White) Ingjaldsson (King of Dublin)
Þorsteinn (the Red) Ólafsson (King of Scotland)
Þorgerður Þorsteinsdóttir
Hrútur Herjólfsson
Þórhallur Hrútsson
Halldóra Þórhallsdóttir
Guðlaugur Þorfinnsson
Þórdís Guðlaugsdóttir
Þórður Gilsson
Sturla Þórðarson
Helga Sturludóttir
Gyða Sölmundardóttir
Helga Nikulásdóttir
Einar Þorláksson
Ónefnd Einarsdóttir
Narfi Vigfússon
Halldóra Narfadóttir
Narfi Þorvaldsson
Valgerður Narfadóttir
Narfi Sigurðsson
Árni Narfason
Jón Árnason
Halldóra Jónsdóttir
Halla Sigurðardóttir
Jón "eldri" Jónsson
Jón Jónsson
Jón Jónsson
Páll Jónsson
Einar Pálsson
Páll Einarsson
Steingrímur Pálsson
Einar Steingrímsson