PicPieBefore adding the widget
Open PicPie, sign in and create or join a Pizza. Check that the Pizza appears in the app. The widget needs access to a Pizza belonging to your current account, so a widget left over from another account may need a new selection.
Add it to the Home Screen
Touch and hold an empty part of the Home Screen. Open the widget gallery using Edit, then Add Widget, or the plus button on older iOS versions. Find PicPie, choose a size and add it. Leave enough free space on that Home Screen page. Finish editing the Home Screen when it is in place.
Choose the Pizza
Touch and hold the PicPie widget and open Edit Widget. Select the Pizza you want to display, then tap outside to finish. If you use more than one Pizza, give each group a distinct name so the choice is obvious. You can add another widget for a different Pizza.
If it looks empty
First check the selected Pizza and your signed-in account. Then check whether there are photos available for the widget. The first image download may take a moment. If the app has the right photos but the widget is behind, open PicPie once and allow the phone time to refresh its widget. Repeatedly removing and adding it is not the first troubleshooting step.