there is discussing day, choosing day, war day, and rewards. There will only be 5, 10, 20, 30 participating in war. The war will last three days.
Discussing Day: During discussing day your team will discuss who to attack in the war chat. To access the war chat you must simply go to builder base and press the button with Two axes making an X, this will be to war button. there will be a red circle on the top right hand corner of the war button, if someone had sent a chat. The reason for having the war chat is to separate it from the normal chat. If Supercell thinks that it is a bad idea, then Supercell shall remove it . You have to discuss to your team who you will attack. You can also look at the builder halls of your opponents and you can visit their base to see how it looks during discussing day.
Choosing Day: Choosing day is when you choose an opponent to fight against. Lets say that # 2 chooses # 3 to attack when attack day starts, now # 3 is forced to fight # 2 because # 2 chose first. You cannot look at your opponent's team's bases during choosing day, It will be your responsibility to look at an opponents base. You also have to remember your opponent's username. You will choose the color and pattern of the flag. You are choosing for you and your opponents. The point of the flags is to see who your teammates are supposed to attack
War Day: When it is War day you are only aloud to attack the opponent that you chose during choosing day, Same goes as the opponent. there will be flags on top of each builder hall. You and your opponent will have the same flag. there will be 10 colors followed by two pattern flags. Red, Orange, Yellow, Light green, green, Cyan, blue, purple, Brown, and White. If there are 20 people participating then there will be 10 people with striped flags and the 10 others with just a plain color. if there are 30 people participating then 10 people will have a zigzag pattern on their flag, 10 people will have a striped flag, and 10 people with a plain colored flag.
Reward Day: During reward day, you are rewarded 1/4 of both gold and elixir of the maximum loot that your base gets, Only if you win the war and if you destroy the same builder hall level as yours, and if you get two/three stars. You get 1/5 loot if you get ONE star to the same builder hall level as yours. If you lose however you will get half of how much the winners get. I don't have time to list the whole rewar because I keep getting confused with how the reward works, But if you attack a builder hall lower then yours then you get less, while attacking a higher level builder hall will give you extra.