To be honest, I typically use a vector graphics app like Adobe Illustrator to create color separations.
That said, Photoshop is pro-level raster editing software for creating pixel-based artwork. It has a steep learning curve, much like a musical instrument -- not something you will pick-up overnight or in a weekend like Canva.
If you wish to be proficient with Photoshop, please take some time to study tutorials to learn about the various tools and techniques first. This is required learning.
https://creativecloud.adobe.com/cc/learn/app/photoshop
https://helpx.adobe.com/photoshop/user-guide.html
Investment in structured online courses is also recommended. Photoshop courses can be found on linkedIn Learning and Udemy.
Practice, practice, practice with inexpensive materials before you plunge into costlier production work. This describes some basic preparation for commercial printing.
https://helpx.adobe.com/photoshop/using/printing-images-commercial-printing-press.html
I hope this helps. Learning Photoshop is a valuable skill to have. Enjoy the process.
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