Make sure your Kontist app is up to date.
Log in to your Kontist app.
In the main menu, go to "Accounting automation".
Under "lexoffice" you can connect directly to lexoffice.
Using your phone's web browser, you will be directed to the lexoffice homepage, where you log in with your lexoffice credentials.
You have to allow access for lexoffice and will be redirected back to the Kontist app. Your account is connected.