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 and navigate to the Tab.
Step 2 - Click on the name of the Tab
Step 3 - You can see the information about the Tab. Click on the Settings icon.
Step 5 - Click on theEdit icon beside the name of the Tab. Edit your desired name and click on the Save button.
You are done!