Dear Pooh Bear,
Like Jewels mentioned - ask your T to give you instructions on how to contain the others parts.
When I have 'others' come out, they normally recede when the trigger goes away. Sometimes one of them stays out for ages... but it will settle when the stress levels are down (even if it does take days).
I have no idea how one gets 'containment'. Containment sounds like shutting a part down? Isn't that how we get DID in the first place?
Possum