You can do it in either two ways, put him at C (but remember to adjust your defensive assignments unless he has good inside D and decent RB) or train 1 on 1 for FWDs (slow but will train HN, DV and JS as well). I don't know your player's skillset, age, etc to make a real assessment. But those are the two options worth considering. Training 3 positions is really slow, I won't recommend it.