Follow these steps to add a new widget to your Home Screen:
 

1. From the Home Screen, tap on an empty area and hold until the app icons begin to jiggle.
    
2. Tap the Edit button at the upper right corner of the screen.
   
    
3. Select Add Widget from the menu.
   
    
4. Enter the name of the widget in the search field, e.g. Dog-A-Day.
   
    
5. Tap on the widget name in the search results.
   
    
6. Swipe between the different widget sizes and appearances until you find the one you want to add.
   
    
7. Tap the Add Widget button at the bottom of the screen.
    
8. Drag the widget to the desired place on your home screen.
   

See also Apple's instructions here:

https://support.apple.com/en-us/118610