How to add image watermark using SixLabors Imagesharp package in .NET core

Question

The code being used to create image using SixLabors.ImageSharp(1.0.0-beta0006) nuget is as below

using (var image = Image.Load(filePath, out var imageFormat))
{
    image.Mutate(imageProcess => imageProcess.Resize(new ResizeOptions
    {
        Mode = ResizeMode.Max,
        Size = CalculateDimensions(image.Size(), targetSize)
    }));
    var pictureBinary = EncodeImage(image, imageFormat);
    SaveThumb(thumbFilePath, thumbFileName, imageFormat.DefaultMimeType, pictureBinary);
}

I also want to add an image watermark on the current image with some opacity. I tried several ways but was unable to do it. Please let me know how this can be done.