The year is 1100. Pick a region to rule with absolute authority. For example you could not pick Spain, but you could choose Castile or Leon. If the country is small enough, like Aragon then you can have the entire country. Conquer your neighbors or be at peace and be conquered by them instead. Remember the best defense is offense. One of your greatest threats is rebellion by the peasants, so you must strive to make them happy.
Germany was inherited by one of Charlemagne's 3 sons. Another got France, and the other got land in between which France and Germany quickly gobbled up. And no you are not the Holy Roman Empire.
Venice is Italy, the map just didn't have their faction.
You have to draft peasants to make soldiers and soldiers have to be trained to make real units. Others will be added later. Be nice to the Pope or he will excommunicate you.
