I am trying to integrate amazon skill kit in my website without an amazon echo unit. I want to implement voice commands on my website using the laptop/PC microphone instead of a
Generally speaking, once you set up your Alexa Voice Service (AVS) client, either on you desktop/laptop, webpage, Android or Raspberry Pi, you should be able to use the AVS client just like the way you use Echo.
Here's the official AVS sample app, well maintained and documented: https://github.com/alexa/alexa-avs-sample-app
As to Alexa Skills, note that "skills" are just like apps for Amazon Alexa. You login your Amazon account, install (enable) the skills for your Alexa service. Then whenever you speak to AVS with the pre-defined command corresponding to a certain skill, it will automatically redirect your command to that skill.