FS Connect is a program that will run alongside MSFS 2020 to sync information about where your plane is in this big 'ol world. Download and install the app and run it when you startup MSFS to get started. You'll need to login with your account credentials you created in the FST Mobile App.
On your guided tour through Middle Earth we have all kinds of extra scenery to help guide you along the way. Once you've logged into FST Connect you can download the scenery pack from the app and install it to your Community folder.
For Windows Store (or Xbox Gamepass) installations you can find it here: C:\Users\[YourUserName]\AppData\Local\Packages\Microsoft.FlightSimulator_8wekyb3d8bbwe\LocalCache\Packages\
For Steam installations you can usually find it here: C:\Users\[YOUR USERNAME]\AppData\Roaming\Microsoft Flight Simulator\Packages\Community