Tvheadend

Hi, I'm new in tvh world.
I install it and configure all, it works good.
I can watch FTA channell with a USB DVB-T stick.

Now I want watch decrypt channell.

This is my situation:

I have a dreambox at my home with a mgcamd server, now in my holiday home (where I install tvh) I want to watch
th dvb-t decrypt channel.

I put a line in Code World Client of tvh with the IP of my dreambox the port ecc... and TVH connecct to it correctly, infact, it is green colored.
But if I try to watch a crypted channell it say no descrambler.
Why?
What do I wrong??

I must install OScam or I can just use the embedded CWS in TVH???

Hope in answer
Thank you so much