Once the battery is loose slowly lift it up so you can get to the terminals as seen in the next picture.

Desolder the battery's connection terminals from the motherboard.

If you do not know how to desolder look at this soldering and desoldering guide

Remove the battery by pulling it out of the device.

In order to avoid damage to the device, the battery must be physically removed from the device before proceeding with any further repairs . Leaving a battery close to a device being worked on can be extremely hazardous. Leads can bump into the motherboard or into each other by accident causing damage to the device.