I think you are looking for the "AC coupling" setting.
I'm too lazy to look up the device, but Hantek and 200MHz make me believe it should have "AC/DC" or "AC coupling" written on the case next to a button.
Basically you are telling the scope to either measure everything (DC coupling) by applying "a straight wire" from input to measurement system (whether analogue deflection or ADC), or measure only the AC content (AC coupling) by effectively putting a galvanic separation between input and measurement system. Much like the decoupling caps on analogue amplifiers and such, only with a more rigidly controlled impedance matching, I'd expect.
(paraphrasing of course)