Hard stuff, need help

[Roroyoyo]

So, this would be my second personal build, even though I’ve had experience and dabbled in cellphone repairs and computer upgrades. Regardless, I build a slightly older pc, one with AMD AM2 specifications. I went for a low power build due to it only needed to be small and fit in a tight space while managing to output 1080p video streaming. I got the ram, hard drive, cpu i believe is a dual core, i bought a new old mono, gigabyte and hooked up a 750w power supply. It starts, fans spin and it gives off a healthy hum. It works and it gives off a signal through hdmi to my monitor, but it doesn’t wake up. I tried hooking up the usb keyboard that I have, a razor deathstalker 2014 edition, but I’m guessing without the installed drivers, I can’t wake anything. How would I be able to wake the computer to display an image and finally get it to boot?