1. Start by finding/making a button base you like, then add your sitename to it. Here's the button I've chosen to use:
2. Dublicate the once, so there appears two identical buttons next to each-other. To dublicate, you have to click on this:
3. Zoom into the second frame. Then use the Text tool, which looks like this: .
Now, write your website name in the exactly same size and font as you did before, but remember to select another color, when you're doing this, because if you have the same color to the text on both buttons, this effect will not work.
4. Save your button and you're done, here's my result:
. 
