Remember to use your basic menu first to edit any of the following aspects of your picture:
- tints and hues
- lighting and contrast
- vibrancy and saturation
Use the HSL / Colors / Greyscale Menu to selectively saturate/de-saturate certain colors from your picture.
Use the brush tool to change only certain parts of your picture. If you do not wish to, for example, de-saturate the color blue from your sky, but de-saturate it elsewhere, the brush tool is a powerful part of Lightroom that will allow you to do so. It can change almost anything.
If you wish to add a vignette, remember to use the Vignette Menu, it has several different option bars for you to get your desired results.