Guidelines on how to make skill matrix for each department. I don't know where and how to start

Hello, I' am a newbie here. I think this site would be found helpful to us. I got a lot of ideas and knowledge that help me perform my duties.
But now I' am having a hard time doing employees skills matrix for each department. I don't know where and how to start.
I hope you could help me accomplish this project.

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Everything you need is already here. Just search and you will find it.