Before you proceed, you need Spaces installed on your phone.
You can change the privacy setting within the first 24 hours of the creation of the Space.
How to change the privacy/visibility of a Space?
Step 1 - Open the Space for which you want to change the privacy and click on the three-lined menu icon located on the top right corner of the screen.
Step 2 - SelectSettings.
Step 4 - Under the Privacy section, select the one based on your requirement - Private/Semi-Private/Public. When you are done, click on the right tick button located on the top right corner.
You are done!