tight bore inner barrel

[nicksaber]

hello evry body i dont ask you guys mane questions but i do need a bit off help with a a WE M4 QCBR .
I am trying to replace the inner barrel with a tight bore inner barrel .

Took top recivier off and bolt out .
Now take me from there please ?
From u tube vids which arnt about my gun they just pull out .
but mine look firmly placed .