For Glossiness you should use the Reflectance Channel and put your texture in the corresponding parameter.
By default there is only a Blin Specular Layer. Change it to a Diffuse model and put your texture there.
Play with the parameters to see how the base material behaves with your lighting.
Create a second layer and add a GGX or Blin Legacy Layer and move it above the diffuse layer. The GGX model is more physically accurate. The Blin is more basic.
If the texture is too noisy disable the diffuse layer and use texture in the Color Channel.
WARNING: To have a nice reflection you have to have also a nice lighting setup and some good knowledge of the rendering setting and models. I don’t know your level of expertise on C4D or the level of quality of the final image you want to achieve so I can’t help you further but all the Glossiness attributes you seek are in the Reflectance Channel and are referred as Specular.