I'm gradually learning more and more in working with Adobe Photoshop Elements 10 and Adobe Lightroom 3 (both programs which I recommend for any photographer who is serious about their pictures). One of the "big things" right now with photographers is creating a watermark. You can do this easily in Lightroom if you are just looking for a simple watermark.
First, import your image to Lightroom.
After you have edited your picture, export your picture (under "file>export").
In the window that opens, you have various options. Scroll all of the way down until you see the option "Watermarking."
You will need to create a new watermark (or, if you have a watermark already - like I do - click to edit watermarks at the very bottom).
A new window will open. Notice that I circled the place where you will type in your watermark. I did "www.withajoyfulnoise.blogspot.com"
On the right, notice that you have various options: Image options (if you want to get advanced and have a logo instead of text), Text options (where you can select different fonts, styles, etc.) and if you scroll down . . .
. . . you will notice Watermark Effects (opacity, layout, etc.).
From here, you will play around with your watermark until you have placed it where you like, have it large or small enough, and so on. Just play around with it.
When it looks pretty, select "save." It will pop up with a screen for you to title your watermark - this makes it easier the next time you decide to watermark you pictures: it will be there, ready and waiting.
Export your picture as usual and there you have it! Your picture has its watermark!
"Now the end of the commandment is charity out of a pure heart, and of a good conscience, and of faith unfeigned:" (1 Timothy 1:5)