Watch this video tutorial or follow the instructions below:
1. Create your widget and tap "Save"
2. Go to the home screen and long tap on the homescreen (so that all the icons start wiggling)

3. Press on the plus symbol (on the top left or top right)

4. Look for "Flex Widgets" and tap on it

5. Select the size of the widget you just created (important: this size needs to match the size of the widget you created!)
6. Tap on the widget on the homescreen (or long press on it if the icons aren't wiggling anymore)

7. Select "Edit Widget"
8. Choose the name of the widget you just created
That's it. If you want to know how you can keep your widgets up to date, view this tutorial.