Ok - how on earth do you setup collaboration

we are using omniplan 2
i have configured the publishing and settings - it test ok
i go to the omni sync server - have an account, obviously otherwise it would not test

what do we do with the person who is trying to collaborate?
how do they get the file

the guy on the demo video setting us web design company with his designer friend - make it look very easy to useā€¦ hmmm