Remove the battery.

During installation, note the orientation of the battery—if the connector is on the same side as the motherboard, and the text is upside-down relative to the rest of the phone, you've done it correctly.

Use a few strips of thin double-sided adhesive tape or a pre-cut adhesive card to secure the battery. (Or, if you are replacing the display, it may come with adhesive for the battery pre-installed.)