This seems to be an easy question but if you look at it, it is hard to solve, for several reasons. Maybe you can post a screenshot of a game in which you saw outlining that fits the style you want to achieve.

In the Gamestudio shader library is a toon shader, which creates an outline. If you want the model to be shaded regularily, comment the lines at the end of the "toon.fx" shader file (in ..\code) in which the PixelShader is called (lines 92 and 124). You can preview the shader in the shader viewer (see \projects\shadertest), but the model is too bright, you have to set the material settings to lower variables, I guess.