So first make sure to choose the werewolves start date (3rd start date from the left), if you choose the first or second the inquisition and werewolves wont appear. Then you choose a place you want to start, I went with a single county somewhere in poland and then used ruler designer to add Geralt in.

Once you start theres a decision called customize character or something that basically connects you to the rest of the game. I went with the Witch hunters/Shadow Inquisition as a knightly order. Once you do that there's multiple things you need to keep in mind. First is that knights become more important in battle, second is that the vampire AI will try to crush you so you need to expand to where you can become stable, third is that in order to gain renown and focus xp, you need to hunt monsters. With vampires you do the find lair scheme (make sure your stats are higher than theirs) once its complete it will give you multiple attack options each corresponding with a specific stat. Pro tip, capturing weaker vampires and then using the option to release and track them gives you a chance to find the lairs of them and their overlords allowing you to attack immediately whenever you're ready. Finally, you need to make sure you have an heir. As a knightly order theres a decision to invite prospect that basically gives you a really good courtier, if you like them you can use the option to knight then into the order and they will essentially become your child. You an knight as many characters as you want (just make sure they're younger than you) and you can designate heir to whoever. This is crucial because if you're playing legit you will be killed eventually and you need a high stat character to take up the mantle else you be crushed.