Built pc, but prots isn't working.

Hello, Reddit. I built done my pc like week ago, and for some reason i'm not able to connect monitor/usb cables to it. Haven't wen't to any repair service yet, and can't find soulition to fix my problem, i'm really sad, had to wait for new mobo first, got it built all and now can't connect monitor and usb cables to it. When i turn it on all system is running well, can see CPU, video card and cooler is working ;) . I really need help.