Let's say you have item A and item B and you want to pin A to B
Select item A in the layout editor and add the PIN behaviour
Now in the event editor create an event that you want to use to actually pin the items. You could just use AT START OF LAYOUT
Then for that event create a new action and click item A. Select PIN TO OBJECT. In the next box select object B as the object to pin to and ANGLE ONLY as the mode.
That's it. From now on the items will move around together.
Once item B is where you want it to unpin from item A you just check using an event for item B. It's as simple as creating an UNPIN action for that event.