You install them, you connect them, you configure them, you use them!
You can install as many network adapters as you please. That said, the reason most ppl consider this move is in the hope they can increase throughput by having multiple network adapters to the SAME network. The short answer is, it won’t work. Windows will only use ONE network adapter for any given network. Any other network adapters to the same network are IGNORED. So it only makes sense to use multiple networks adapters if they're bound to completely different networks.