You can change your starting weight following these steps:
1. Go to your Start page.
2. Click "Edit Goals" under the button to track your weight and other measurements.
3. Scroll to the bottom of that page. At the very end you will see the place to change your starting weight and also adjust the date if necessary.
4. Click the button to save your changes.
*Note: Doing this will cause SparkPeople to recalculate your calorie range based on all your current information and adjustments will be made only if necessary.
I hope this helps!