Tap the edit icon (pencil) at the top right corner of the header.
Click on the plus icon (+).
Use the search bar to find your desired index.
Tap the plus icon next to the index in the search results to add it to the
header.
2. Deleting an Index:
Tap the edit icon (pencil) at the top right corner.
Locate the index you wish to remove.
Click the dustbin icon next to that index to delete it.
3. Replacing an Index:
Tap the edit icon (pencil) at the top right corner.
Find the index you want to replace and click the dustbin icon to remove it.
Tap the plus icon (+) and search for the new index.
Once found, tap the plus icon next to it to add it to the header.