The good thing about my local hardware store is that they cut the pieces of wood for you and this made our job a lot easier. If you cannot get it pre-cut then you can just follow the measurments listed earlier and then carry on.
Building the headboard is very easy when you're at this part. MDF needs to be pre-drilled like any other wood before screwing it together, so always drill a hole first and then screw it together.
The next step that I did was to create two holes for the speakers that I was going to put in the headboard. I basically just measured around the speakers and then built boxes out of MDF to hold them in place.
After building the boxes it's a good idea to drill holes in the back for wires to go through.