1. **Installer**
Under Windows, you can download a small installer that will update Picasa for you: Installer.
2. **Manual Installation**
With the latest version of Picasa, you can copy the Button file into the buttons directory of Picasa (typically `C:\Program Files\Picasa2\buttons` on Windows). For older versions, such as on Linux, you need to modify the file `runtime/btnconfig.xml` and append the following lines:
```xml
Send To Flickr!
Upload your photos to flickr
```