I don’t have the symbol on my Home Screen to add widgets
I can’t add widgets to my iPad Pro because when I press the Home Screen to get the app’s jiggling the plus sign does not appear on the top left of the screen
It doesn't work the same way on iPad as it does on iPhone. Swipe your home screen to the right. That's where the Widgets are for iPad. Then press on any widget to bring up a dialog box to add or remove widgets to your liking.
If you want to have Widgets on the screen always, you want to go to Settings > Home Screen & Dock and turn on Keep Today View on Home Screen (Note: Today View only works in Landscape, not Portrait).
See this link for more details --> Add widgets to the iPad Home Screen - Apple Support