I'm very new to Blender (I use Blender 2.8.3). I give my objects some texture but I don't know why the texture won't show up both in the viewport and when I render it.
. How ever, the other texture (
) has no problem. I've tried this way from https://artisticrender.com/blender-viewport-shading-guide/. But I think already have my 
(or haven't I?). Thank you in advanced.
The most common problem is that we can't see a texture or color that we added to our shader. This is most often because we are still stuck in solid viewport mode. To resolve it, just change from solid viewport mode to material preview mode in the top right corner of the 3D viewport. Material viewport mode will set up a default lighting with no shadows so that you can see your materials in full. There are a few settings related to this viewport mode as well that we will cover later.
Under Object data properties you can find a tab for UV Maps. The Addon (OSM) you used comes with some UV Data so you simply have to remove the old data by clicking the minus icon and then unwrapping it yourself. I know this is 2 years too late but perhaps someone else runs into the same issue.