If you purchased it online from Steam, you can start MSFS from Steam platform directly.
If you purchased it online from Microsoft store, steps are as follows:
--->Firstly, please install Pimax Experience.
1.Please select Experience Home in Pitool, then you will be prompted to install Pimax Experience:
--->Secondly, you can import the game to PE. For more details, please refer to:
https://community.openmr.ai/t/importing-fs2020-gamepass-version-into-pe/34046