- Go to Appearance -> Customize
- Change the active theme to the desired new theme
- Click Live Preview
- Once in the new theme, click on Appearance -> Widgets
- Scroll to inactive widgets
- Reassign all the widgets from the previous theme to the Home Page Widget Areas in the new theme
- Make sure all widgets are in the areas you would like ( sometimes the Footer and Social widgets can be left inactive as well. If this is the case, reassign those widgets as needed )
- You can upload a header background image as Featured Image
- Click Manage in Customizer
- Scroll through the theme to see if the widgets are all in order
- Press Save & Publish