How to watch the ROKU channels on you PC

That cannot be done. The Roku player is designed to connect to a display via an HDMI connection. While your computer may very well have an HDMI connection, it is an output jack, not an input. Only a highly specialized computer set up for video processing would have video input jacks of any kind. You might be able to connect your Roku to your computer monitor (assuming the monitor has an available HDMI port), but then you're simply watching the Roku and your computer is inaccessible for viewing. 

Now, depending on the provider you're desiring to watch, it might be possible to view the provider's content on a web page. You can certainly do that with Prime Video, Netflix, YouTube, and even The Roku Channel. But your Roku player won't be used to view the content in this manner.