There is a menu, where you can tune such parameters as:
Effect Channel (Hue, Saturation, Brightness), Effect Operator (Derivative, Gradient), Effect Convolve (With white noise, with source image),
Filter length, Noise magnitude, Integration steps, Minimum or Maximum value.
To apply Van Gogh effect:
1. Load photo/image,
2. Go to menu Image Improvements > Van Gogh,
3. Tune the parameters.Samples with white noise and source image parameters: