You should use InfoPlist.strings file (keep both I & P capital) to localize values of Info.plist. To do this, go to File->New->File, choose Strings File under Resource tab of iOS, name it InfoPlist, and create. Open and insert the Info.plist values you want to localize like:
NSLocationWhenInUseUsageDescription = "Description of this";
Now you can localize InfoPlist.strings file with translations.
Select the localization options, or enable localization if needed,
You should be able to see the file also on the left side editor.
NOTE: When testing the localizations on the simulator. You have to change the language on the simulator itself not just the language in the Xcode target. (Credits to John Webb)
Here is the official documentation for Info.plist keys localization.
Credits to Marco, thanks for including the pics in this answer!