You can bring someone to collaborate on your spaces by inviting them to the organization the space belongs to.
You can generate invitation links with different permission levels:
Readers: Can only visit the published spaces in organization, including private ones. They cannot edit, and cannot see changes that are not yet published.
Writers: They can read and edit spaces. They can see drafts and changes that are not yet published. They can publish changes. They cannot edit the organization settings, nor the spaces settings.
Admin: They can do everything writers can do, plus change the organization and spaces settings.
Once you have generated an invite link, share it with people you want to invite.
If you were given an invite link to someone's organization, you can visit it to join the organization. If you are not signed in, you will be asked to sign in. Otherwise, make sure you are signed in with the right account before proceeding to join the organization.