move subforum topic

i already use that multi forums in one.. so now my problem how can i move my topic to that multi forums...

i think i can just that topic to a blank one but it cant move to my the subforum

example like this..

i want to move a topic in a Announcement sub forum to a multi forum.. i want to make a Announcement in that multi forum so i try to move the topic .. but im confuse how to move it.. if i move it to a blank one the topic is not in the Announcement that i make in the multi forum..

so how can i move that topic to the purpose forum

You just post a new topic.