The process for reinstalling the free version of the app is slightly different depending on where you originally downloaded the app. Below are instructions for purchases from Google Play and from Amazon.com's Appstore for Android.
Option A--Purchased from Google Play Store/Android Market 1. On your device, open the Google Play app.
2. Click the menu button on your phone.
3. From the options that appear, select "my apps."
4. At the top of the page, you will have the option of viewing installed or all apps. Click the button that says "all" to view all apps.
5. Scroll to find the app.
6. To the right of the app title, click the icon that says "free" to install it.
Option B--Purchased from Amazon
1. Open the Amazon Appstore App.
2. Click on the menu button on your phone.
3. Form the options that appear, select "my apps."
4. At the top of the page you have the option of viewing new, installed, or all apps. Click to view all apps.
5. Locate the SparkPeople app from that list and click to install.
If you want the paid version of the app (which has enhancements the free app doesn't), then you'd have to pay for it.
Hope that helps,