How do I stream from my TCL Roku TV to my Lenovo P51 laptop?

I have tried plugging an HDMI cord into both my tv and computer, but all I can manage to do is screen mirror my laptop onto m tv. I want to use share screens on Skype from my computer so that my friends can watch me play video games on my Nintendo Switch which will be on the tv. Any ideas?

The HDMI ports on your TV are INPUTS, the HDMI port on your laptop is an OUTPUT. Signals go from on OUTPUT to an INPUT it does not work in reverse!

In order to get your video into Skype on your laptop, you would need a suitable capture device between your switch and the TV that then linked to your laptop, and is recognized by Skype as a camera.

SO with extra hardware, it's possible! Just one question though, do you really think your friends are that interested in watching you play games?

You don't.

TVs are not output devices. That is, they do not send signals to your laptop or anywhere else for that matter.