You don't use textures to place lights in Hammer. You use the entities "light" (omnidirectional) and "light_spot" (more realistic, cone-based light) to place lights.Nevermind, I found out.
https://developer.valvesoftware.com/wiki/Adding_Light (https://developer.valvesoftware.com/wiki/Adding_Light)
texturepath/texturename 250 240 205 100