Sharing Spaces works similarly to sharing projects. The unique part of sharing a space is that the Portfolio Layer inherits each member's project permissions individually.
In other words, space members can only see the projects that have been shared with them. This means that different space members will likely see different project lists based on the governance of different projects.
The most important thing to remember is projects do not belong to a space. Projects live in the workspace only. Spaces are special curated views of data, and the portfolio layer adheres to the governance of projects & the workspace rather than overriding sharing based on the space settings.
You need to be an Admin of the Space to share it
To Share a Space:
From Share Menu
Click the share icon in the top right
Input email, select a team, or select a workspace to share with:
From Space Settings
Click the Gear icon on the left.
Click the Shared-With icon
Input email, select a team, or select a workspace to share with:
From Bulk Share Projects
Select multiple projects from the Data Table, and select share.
Share with individuals, teams, or workspaces.
Select if the space should be shared also:
Only share selected project: Projects will be shared but shared_with will not have space
Share this space and selected projects: Projects will be shared AND shared_with will have space