Mono-addition of HCl to unsymmetrical dienes?
Do we agree that the first step ist the addition of a proton to the diene? This is bit different from the addition of HCl to an alkene, where you would rely on the Markovnikov rule. 

Here, stabilization of the cation through resonance comes into play.


  I don't know how to draw it [...]


Draw stepwise!



In principle, a proton could add to one of the positions a to d.

How do the resulting cations look like and which of them are stabilized by resonance?



Is it now a bit more clear?