After removing the mainboard, the battery should be in full display.

Easily pry the battery from the right hand side, careful not to insert the prytool too far, the device's LCD is directly underneath the battery.

Seat in the new battery, if it doesn't fit perfectly, do not bend, pinch or puncture the battery to make it fit, some corners may need to be pressed in, be careful.

Reseat the battery connector, using adhesive if the part does not have it behind the connector.