Step 1. Long tap on the home screen. Either on some icon or on empty space.

Step 2. Tap Plus button:

Step 3. Select Themes app:

Step 4. Select Small or Medium widget depending on theme and tap Add Widget button:

Step 5. Tap on added widget:

Step 6. Tap on Widget row:

Step 7. Select necessary widget from a list:

Step 8. Tap somewhere on a screen. All done. Enjoy!