You have to select the correct layer first to edit it/paint it or whatever. And by lines I think you mean the wireframe, you need to deselect that layer by removing the eye icon in the layers panel.
The layers panel is normally in the botton right of Photoshop if that's what you're using.
You need to do some basic tutorials, this should teach you about layers and how to select or hide something. Go back to master skinnerz and look in the tutorial sections that are there, the tutorials are on Photoshop not "how to skin" but you need the basics to get started.