To install the Photoshop patterns:
Download Patterns. Find the patterns that you want on the web and download them to your desktop. The Adobe Photoshop patterns file will be in a .PAT format. In this case, they will be zipped in a .ZIP File
Unzip the File. Adobe Photoshop (any version)/ Presets/Patterns/ here they go
Load the patterns. You can use the patterns double clicking on any layer to access the Layer Style dialog box
More links about installing and using Photoshop patterns:
https://www.webfx.com/blog/web-design/photoshop-patterns-ultimate-guide/ https://www.dummies.com/software/adobe/photoshop/how-to-apply-a-preset-pattern-in-photoshop-cs6/
NOTE: Basic knowledge on the use of Photoshop patterns is recommended.
Enjoy!!!