You don't, Confluence permissions are permissive - you allow people do stuff in spaces, not set flags to stop them in general.
There's also the layer of page restrictions over the top of that, but they're done by page (and cascade to child pages), not at a top level.
You will need to remove whatever is granting your users general access, re-adding the ones that are needed, and then leaving the spaces you want hidden off the general list of accesses.
Hi my Community friends! For those who don't know me, I'm a product marketer on the Confluence Cloud team - nice to meet you! For those of you who do, you know that I've been all up in your Co...
Connect with like-minded Atlassian users at free events near you!Find a group
Connect with like-minded Atlassian users at free events near you!
Unfortunately there are no AUG chapters near you at the moment.Start an AUG
You're one step closer to meeting fellow Atlassian users at your local meet up. Learn more about AUGs