In order for Hightouch to sync data to Freshsales, you need to give Hightouch an API key and subdomain so that Hightouch can update your records.
You can retrieve your API key by navigating to Settings > API Settings:
For subdomain, check the domain that you are logged in, it should have the pattern of https://yoursubdomain.myfreshworks.com. The subdomain used to configure the destination is yoursubdomain.