This is one of my favourite little tricks to completely change the dynamics and atmosphere of a photograph. This process is extremely simple and requires just the use of brushes and correct exposure.
Really all you need to do is first darken the image, to give the appearance of a closer time to sunset. Now first use a clarity brush to enhance the foreground, this will also enhance any lens aberrations and so create warm specks later on.
Next we move onto temp brushes. Now the warmth you select for this brush will depend entirely on the pre-existing white balance of the photograph. You should set the brush to 100% feather and reduce density and flow to about 80%. Making the brush fairly large, brush along the entire horizon. Then readjust the temp level to select the desired amount of warmth.
Finally we want to give the impression the sun is in the correct position. Earlier we darkened the entire image, now we want brighten up the far right. Using a dodge (lighten) brush set at about 0.50, the brush wants to be even bigger than the temp brush, keep the feather, flow and density settings the same. Then just brush in a circle and adjust the exposure accordingly once applied.