Before you proceed, you need Spaces installed on your phone.
How to rename a Tab?
Step 1 - Open the Space in which you want to rename a Tab.
Step 2 - Navigate to the Tab.
Step 3 - Beside the name of the Tab, you will see an icon > Click on the same.
Step 4 - It would open up a pop-up showing you the current name of the Tab > Edit the same.
Step 5 - When you are done, click on Save button.
You are done!