To change the word Boutique, you should open supplied source PSD file in Photoshop and edit word there. Then you need to crop it and save as "top_bg.png" in the template's images directory.
Before you try to do that, please open existing "top_bg.png" file in Photoshop to see how it is cropped and organized.
1. Select layer with text, layer 40 and layer 41.
2. Merge them (right-click on the selected layers and Merge Layers).
3. Disable all other layers (including Background layer).
4. Save image for web, PNG24 format, overwrite file top_bg.png