raster - How do I export a 16-bit image from QGIS?

Could someone explain how to export from QGIS a 16bit image.

I have imported data and coloured it as I want, but need to export it as a 16bit image, as 8bit is giving a terracing effect.I believe I need to use this code in OSGeo4W Shell, but I don't know how to use it?

gdal_translate -ot Int16 -srcwin xoff yoff xsize ysize -outsize xsize ysize src_dataset dst_dataset

Here is a screenshot of my map, which has the following extent:

Xmin 510000, Ymin 156000, Xmax 528000, Ymax 174000