From their website:
Before you take command in battle for yourself, you must practice and prepare. The rules for Battles of Westeros (PDF, 5.3 MB) are now on the support page.
Set in the rich and vibrant world of George R.R. Martin’s Song of Ice and Fire series, Battles of Westeros is a board game of tactical battlefield combat for two players. With scenarios that include beloved characters and settings, players can recreate the most significant battles from The War of the Five Kings.