Hello enoc94,
Thank you for reaching out to Apple Support Communities. We are happy to help you!
We understand that you would like to add the Korean language option to the input source on your Mac.
We have provided you with helpful steps to assist:
Type in another language on your Mac with input sources
"Add input sources
- On your Mac, choose Apple menu > System Preferences, click Keyboard, then click Input Sources.
- Click the Add button , then search for a language (such as Chinese, Simplified). If it has an input source (such as Handwriting), select one or more.
- Click Add.
After you add an input source, the option to show the Input menu in the menu bar is automatically selected. The Input menu lets you quickly switch input sources as needed."
We hope this finds you well!
Cheers!