Don't. CPU mining will get you two things these days: jack and squat. You will make a cent or two per month mining BTC with that CPU. Not a bitcent or two, a USD cent. If you're lucky.  Likewise, nVidia GPUs are not good for mining.

Mining puts stress on components, which increases heat inside the case, which adds yet more stress to the components.  Those slimline PCs are a bitch to keep cool even when you're not doing CPU or GPU intensive operations. I know, I've owned a couple.  Good little entry-level, general purpose PCs, good for browsing, Microsoft Office, watching movies, but not much else. They make an OK DLNP media streamer if you attach some USB hard drives to them.

if you want to use that box for mining, pre-order an ASIC device and run it off that PC. that's the only way that machine will generate any bitcoins for you.