Hi SORINfromMD
Like Windows 10 you can set the drive for the installation of modern (UWP) apps in settings -> system -> storage -> Where new content is saved
select the HDD from the dropdown under "new apps will be saved to:"
Older desktop programs may still offer the option to choose a path but the modern apps don't, you can only set the drive in settings.
you may get better performance when opening and running apps by saving to the SSD and using the HDD for data