I've done this job on my other BMW's. Really simple that you probably don't need pictures on this one.
If you were going to flush the radiator, might as well flush what's left in the block too (there's another plug as other members mentioned). Quite a lot of coolant came out of that too.
Be prepared to get soaked though. It's always such a messy job. I recommend wearing safety glasses and have plenty of towels/rags on hand.
Current: 2008 BMW M3 Sparkling Graphite/Bamboo Beige/6MT. 1999 BMW M3 Techno Violet/Dove/5MT. Next: 2017 BMW M3 Austin Yellow/Cloth/6MT