your problem is:
there is more than one method to put a texture onto a mesh/object!
using the texture-option of an object(needs the uv-unwrapp set for a texture-image)
using a material with an texture-image mapped in different default ways
using a material with multiple texture-images mapped and combined
using multiple materials…
using a texture-image projected dependend on position, rotation, scaling…
most people use a material with a texture-image, it is more flexible.
for minimalistic use, load image in uv-editor, uv-unwrap object with this
image and enable the check-box for this object to use texture. But like said,
most people want use this and therefore most tutorials explain the way to set
a texture in the material-settings.