First, you need to have one good procedural material.
You can see I used a wave texture link to the Principled BSDF node and this to the default material node.
This will create procedural material with distortions.
If you want to create a texture for your object you need to use these steps:
- Select Render engines with Cycles;
- Add an Image Texture node into the node area;
- Select this image in the Image View area;
- With this active image texture node, select on Bake area – Bake Type to Diffuse and press the Bake button.
After that, you can save the texture from the Image View area with Save As or using short keys: Alt + Shift + S.
You can see in the next screenshot where are these steps: