The international version of Hancom Office 2020 does not include Hangul Word Processor (HWP) so if you need to edit HWP files you will need to try the following alternatives:
1) Purchase HWP from Hancom's Korean online store.
It's available in Korean language only and a perpetual license for the home & student edition is available at https://www.hancom.com/goods/subMain.do. Please note that only Korean credit cards are accepted.
A perpetual license of Hancom Office with HWP for Business is available for purchase in Korea only because it's a product designed for domestic customers.
2) Subscribe to the Hancom Space service
A subscription license for businesses is available through Hancom Space that includes Hancom Office for Windows/iOS/Android and HWP for Mac.
After subscribing to Hancom Space, you can log in to your account and download and use the Korean version of Hancom Office 2020 that includes HWP.
Hancom Office 2020 (with HWP - Korean) Download Link: