The Rebbe directs him to the teaching of the Tchernerblier Rebbe (and in Hayom Yom, 23 Sivan) to discern between Yetzer Tov and Yetzer Hara. He adds that not only is it permitted, but it is an obligation to learn Tanya with others, as studying Chassidus strengthens Torah observance and mitzvos.
https://www.torahrecordings.com/rebbe/igroskodesh/015/010/5519