Tools required: Phillips screwdriver
Remove your back cover, battery, sim and memory card. At the top of the phone you'll see two little plastic plugs. Lift these out two reveal two screws. Remove these two screws plus the other four you can see.
Starting near the bottom of the phone, run your fingernail, or something like a guitar plectrum, all the way around the join of the battery compartment to unclip it.
Your phone should now look like below.