Setting Foxit as the new default in Windows OS:
Open Foxit App, go to Help > select Set to Default PDF Reader.
Open Foxit App, go to File > Preferences > File Associations > Advanced > check all options > click on OK > click on Make Default PDF viewer > Click on OK to apply the change.
You can also right click on a PDF > choose Open With > select "choose another app" > select Foxit app > check the option "Always use this app to open .pdf file" > click OK to apply the change. For more specific steps, refer to HERE.
Refer to HERE for specific steps.