How do I use and HDMI "IN" on Windows 8.1 PC

[bobbybobertiscool23]

I have an alienware pc running on Windows 8.1. I do not know the model and I do not have the manual for it but it has an HDMI "OUT" and "IN" and I'm wanting to know how to connect my PS4 to it and play it through the pc. I have everything connected but I cannot find anyway of seeing what should be playing through the port.

 

[rgd1101]

exact model of this alienware pc?

 

[bobbybobertiscool23]

exact model of this alienware pc?

i beleive it's the Alienware Alpha. It's one of the steam machines.