XF 1.3 creating a new node with permissions

Is there a quick guide to adding nodes with the correct user permissions as having looked all I can find is geeky info on permissions explained lol
I've added several nodes under a node within a category with "inherited" perms and set to visible in forums etc but some show "post new thread" and some don't so it's got to be user group permissions?
I'm sure am missing something stupid and do tend to look too deeply into things :whistle:
Any quick link would be fine thanks :)
I just created a new node as 'forum' under the forum I'm having bother with and it seems spot on, never edited the permissions at at all and post new thread is visible so maybe its got to be individual forum perms gone wrong...