I have Cubase se, what else do I need now?

Preamps usually (I hesitate to say always) have 48V phantom power built in, so yes, it will power your condenser mic. You can then run the preamp to the mixer and the mixer to your soundcard to record multiple instruments. However, I recommend that you take full advantage of your card’s four inputs. If you’re recording multiple instruments, connect them to your audio card’s inputs rather than the mixer, unless you have outputs on each of your mixer’s channels. You can still use the mixer to record things than are okay on a single stereo channel (accoustic guitar, vocals, or some drum mixes.) But if you can get every instrument on a different cubase track, that would be ideal for mixing purposes.