The information on the official website states that Picasa is compatible with Windows XP, Vista, 7 or later, which means in Windows 10 is should work properly. However, since there is no other version available, you should apply a compatibility tweak. Right-click its icon and go to Properties > Compatibility. Choose Windows 7 from the drop down menu and then tick the Run as Administrator. This should improve things a bit when it comes to functionality.