What is the procedure to delete any of my post/thread in my forum?
You sacrifice a Duck to summon an administrator.
There's no way for us ordinary users to do it, sorry.
You can delete a new thread, I think that is a glitch though.
Let one of us Mods know which thread you want deleted. You can PM us with a link or post in that thread requesting it be deleted. (Posting on the thread, itself, is probably the best option, as the first Mod/Admin who finds it can deal with it for you.)
Here's the sticky forum topic about that https://greaterthangames.com/forum/topic/on-deleting-posts-3875