You can both access the Grammarly Editor and set up the Grammarly Keyboard through one Grammarly app on your iPad. The Grammarly Keyboard allows you to get suggestions from Grammarly in other apps.
To access the Grammarly Keyboard, open the Grammarly app and tap Keyboard at the bottom of the screen. Then, follow the prompts to finish setting up.
The Grammarly Keyboard allows you to customize your writing experience. To learn more about adjusting your settings, visit this page.