Help Help! HTC Desire 820 Soft Brick

[Tomislegit]

I tried rooting my HTC Desire 820 and messed it up slightly, and I ended up wiping everything on recovery without knowing what I was doing. When I reboot I get a warning saying no OS is installed, and it just gets stuck on the HTC logo when I try and turn it on. Please give me step by step instructions as I am a noob lol, the only details I can find are:

Software status: modified
Unlocked
A51_UL PVT SHIP S-ON
HBOOT-3.19.0.0000
RADIO-01.01.010_UL10305041_08.01.50512
OS-2.10.401.4
eMMC-boot 2048MB OC
Dual sim

If any more detail is required then please tell me where I can find it, I need this fixed asap. I just want to flash a stock rom to how it was when I first bought it.

Thanks