How do I create a seamless pattern in Photoshop?

This is would have to be one of the best tutorials on how to do it.  In fatc this is the absolute best Photoshop tutorial channel on YouTube.   Also check out View > Pattern Preview

Hi
As you have found, the pattern you are repeating is not seamless. That is easy to address in Photoshop though.
1. With your pattern open, go to Filter > Other > Offset and set the Horizontal and vertical offset to half the width and height of your pattern tile. This will move the edges to the centre of the pattern tile.

2. Now the old edges are centred, paint them out with a brush (or use the spot healing tool) so that those harsh transitions are gone.

3. Go to Filter > Other > Offset and offset the image by half the width and height again. This will put those repaired edges back at the edge of the tile.
Your pattern should now work seamlessly.

Dave

@creative_6146 I haven't created a pattern in Photoshop, but I did it with Illustrator for my fashion students a few years ago. You can watch this, and see if it's adaptable for Photoshop. https://www.youtube.com/watch?v=S_xyNThdGlc