Inside your space, just click on the “members” option and then click “invite members”. You then have a number of ways to invite your collaborators to the Space.
You can share the link with your collaborators, and when they click it they will immediately join the space.
You can also share the Spaces code and they can join by clicking the “+” button in their Spaces panel, and clicking the “got a code?” button. They can enter the code there and they will be able to access the space.