After an item is created you can always change its workgroups assignment.
Step 1:
Go to the item screen for the subject meeting.
Step 2:
On the left side of the screen, find the Item Data block.
Step 3:
Find Item belongs to the workgroups. If your access privileges allow you to change the workgroup assignments, the Manage Item's Workgroups link will appear. Click it.
Step 4:
In the Select Workgroups box, make the workgroup assignment changes you want by selecting or deselecting the listed workgroups.
Step 5:
Click the Set Workgroups button.