Error: Default Compiler Version 5' which is not available.

Getting Error: *** Target 'Target 1' uses ARM-Compiler 'Default Compiler Version 5' which is not available.
*** Please review the installed ARM Compiler Versions:
'Manage Project Items - Folders/Extensions' to manage ARM Compiler Versions.
'Options for Target - Target' to select an ARM Compiler Version for the target.
*** Rebuild aborted.

I've downloaded a legacy ARM_v5 but when I go to Manage Project Items/ Folder and Extension/ there is no compiler there to choose from? Any help would be appreciated. Thank you.