UE4: Making Materials Shiny

1) Edit your material

2) Add a scalar param node with a default value of 1 wired into the Metallic channel

3) Add a scalar param node with a default value of .5 wired into Specular channel

4) Multiply a scalar param node with a default value of .5 (combined with the texture's alpha channel) into the roughness channel 

Lower roughness to increase shine. You can also reduce roughness (or the Metallic value) to reduce the shine. Specular is almost always good at the .5 value.