Experience Points are used to upgrade your attributes that’s why they are important in the game. Deal damage you deal with even if it is melee or throwing weapon as well as the number of health points affects the experience point.
How to get Experience Points Quickly
The most important thing to get Experience in any RPG game is Side Quests in-game. So, if you complete side especially inside the main settlements of individual factions. They are usually the longest quests in the game which rewarded a lot of Experience points.
You can also get EXP while fighting with enemies. More difficult the opponent to kill the better the experience points you get. There is a fact that more powerful enemies are difficult to kill by yourself because if they hit once or twice you will die instantly and you have to restart the game from the checkpoint.
Fighting enemies with your Allies
So it is worth having a campaign on your team that can fight and kill from a distance. Which will help you fight with more demanding and powerful enemies. Once you kill enemies with your allies run toward enemies and hit them to get points and if you and your allies did not hit you will not receive any experience points.