Before you proceed, you need Spaces installed on your phone.
How to add new members to a Space?
Step 1 - Open the Space in which you want to add members.
Step 2 - Navigate to the Members Tab.
Step 3 - Click on Add new member:
Step 4 - Add new without saving the contact number on your mobile phone (click here) or Search the members you want to add. Once added the members, click on the right tick button located on the top right corner.
You are done!