There's 2 ways to make a runway textures in Orbiter 2016 :
The "legacy" one, where you apply a 2D-texture to the rectangle defined as the runway ;
The "newer" one, where you rely on level 19 (very hi-res) ground textures.
There are a couple of addons about KSC and texture packs around. Be sure you have downloaded the stock hi-res texture pack for planet Earth. See "optional high-resolution..." here :