how to adjust the setting of a material? For example… the size of a texture?

TIP #1: Box mapping
  • set rendered mode to visualize the draft of the texture
  • click on the object properties, and then texture mapping
  • click on apply box mapping
  • draw a cube with the dimension of the texture: for example, my texture was a parquet, with 20 listons, each 12 cm wide. The final size of the texture will be a square with side: 20*12=240 cm. At the end you can check the preview to see if the result is correct (obvisouly it is a rough representation, but the important is the final size).

Disclaimer: this is a fast guide, a tutorial, an how-to article that I personally wrote for you. Feel free to write here any kind of suggestion! It is helpful if you need to solve your problem, if you need a tip or if you are in trouble and you need an help!