There are a myriad of different ways of doing this, but here's one (simple) option that doesn't use layers, masking, or anything complicated:
- Open the image.
- Image>Adjustment>Desaturate
- Image>Adjustment>Photo Filter
Change the drop down menu to "Sepia", then play with the density slider to get the effect you want.
Or... Another easy way with a bit more control:
- Open the image.
- Image>Adjustment>Desaturate
- Image>Adjustment>Hue/Saturation
Tick the "Colourize" box, then set the hue slider to about 24 and the saturation slider to about 23. Again - play with the settings to get something you like.
-H