WAR is very "learn by doing". The only things you need to know are really basic, like keeping Storm's Path/Eye up, opening a boss battle with Infuriate -> Unchained, popping Berserk + Bloodbath when spamming Overpower, etc etc. There's a lot of situational uses for all your abilities and you just need to react in those situations with the correct ability. Just remember to have fun and learn as you go~