I cannot access material blue print of a textured material to scale it down in size

How do I open a material blue print to edit it? (I want to scale down a textured material “asphalt” but when I double click on the material in the contents a window opens with a sphere displaying the material and details panel on the right. I do not know how to access the blue print of the material itself. Please help thank you!

you are looking at material instance , on right details panel you can look for parent material in General tab.