The best way is just to take an overnight train "Kyiv - Kryvyi Rih" #76K or others. The train ride is nice and comfortable, with a restaurant carriage.

• By plain & bus (fly to Dnipropetrovs'k and then take a 3 hour marshrutka ride to Kryvyi Rih) (Boryspil airport)
• By bus (for Ukraine bus schedules look here (in Russian)