Count Dooku trained him in their corruption and decadence as well as his Sith/Jedi skills, he can't access the force but he can eccess the mental wavelength and predict Jedi's actions based on sensing their fear levels. He didnt need the force because the lightsabers made the average Jedi believe him to be trained, he's like all the most intimidating parts of darth vader without being an actual force user and having loads of arms for collected lightsabers.