if you can't communicate maybe try journaling? i know for us there was originally different levels of knowing each other. Linn and ell had known each other for years before the entire family realized "oh hey, there are other people here too" - so basically, meeting one person might be a chain to meeting others they know. Like going to a party and meeting friend's of your friend. so there is that.
Journaling is nice because it's a free space for everyone and it has some privacy and also IMO feels safer than verbalizing things sometimes. You could also try some art. or just have general awareness for "loud thoughts". If you don't like the smell of roses but you pass one and in your head "mmmm smells sooooo niceeeee" is being said, inquire about it - cause someone is thinking it (sh*tty example i know but it works).
you could also take what i call the "Sherlock Holmes" approach. so if you're aware of dissociative symptoms, or you come back after, and you sorta focus on the cues or hints of your environment/mood etc you can maybe gain some insight into different people. learning triggers and all that stuff is part of it. (ex: back before i was in the loop, i'd "come to" sitting at this organ/piano. All. The. Time. and i don't play the organ, but it would echo for a few seconds and i'd think, "well that's awfully bizarre. i must have a haunted organ". but ell plays the organ, so the haunt was not external. go figure.)
or just chat in your head. you know, go for it. "What's your name? How old are you? Do you wanna play Skyrim?" whatever it is. maybe they won't answer at first. i sure as sh*t didn't. (though i did curse profusely at Lola) there will come a time when you're in a toy isle or hear a song echoing in your head or a laugh or a snarky comment or an "OMG I want THISSSSS" at a healing crystal shop, when they warm up to you.
i don't know where you are in your journey, but if it's still in the "this makes me insane/i am crazy" stage, some may be less inclined to talk to you. openness and understanding is a good place to start and just send those vibes around ("positive energy of light and love" says Linn). it takes time. it takes trust.
and remember every multiple is different. and every Other is too. some of ours don't talk with words. some sign. some speak a diff language. some are shy. some talk through images. some speak through body language or grunts or whatever. some are preverbal. some just don't want to talk, period. there is no "right way" to talk to head-mates that works for every single multiple. it's a matter of finding what works for you and yours.
Good luck.