Users can learn general information about the app from the landing page, but you can show particular functionality and explain how to use it.
Show the user the content they will be able to access after signing in. Let the user test your app with some pre-built examples of what kind of work your application can do. This way you can demonstrate the value of your app and let the users evaluate its potential
If you suppose that users should have some learning to successfully use the application, create a step-by-step demo. You can make a demo tour or show a video. Give the user a choice: learn more about your app, or start working immediately if they're ready for it.
Don’t overwhelm the user with information. Reducing the number of needed steps is one of the most effective ways to increase your conversion rate. When you develop onboarding, make sure that every step of it provides new information that the user can apply right now.
If a user wants to know more about the app, they can always use the app’s user manual.