1. Check to make sure that LMS/LTI Integration has been activated for your account.
For instructions on how to check, see this article.
2. Log in to your SolidProfessor account and create a new class.
Classes created prior to 5/6/2019 will not display LTI integration settings.
3. In a different browser, log in to your Moodle account and either create a new course or click to enter an existing course.
Be sure you're using a different browser than where you have SolidProfessor opened. Eg. If you have SolidProfessor open in Chrome, you'd want to open Moodle in Firefox. Not opening the apps in different browsers will cause issues with the setup process later.