These three diagrams show 1. The thin sheet metal (yellow) placed between the punch and the die. 2. The hydraulic ram lowering the punch and pressing the metal into the die. 3. The punch being raised and the stripper ring pushing the formed part off the die. Note there maybe excess metal that's needs to be trimmed after forming.
Casings for computers are often press formed. you can see in this photo press recesses for mounting other parts and depressions to take the heads of screws or bolts. this is also a nice example for showing how metal punching and pressing often happen at the same time.