Hi could anyone please tell me how I can  unlock a channel and lock a channel on  buzz tv 6

While on the channel hit red button

Same for unlock 

one thread per topic is good enough

Depends on where you are.  But just look at the button legend typically on screen for the colored buttons.

From the Channel list view, use red button to toggle (as nbs has pointed out above).   While watching a channel, if you press down to get channel OSD, you will see it is the blue button from that screen.   Bottom line, all functions are typically identified in the legends of the various screens.