Please follow the instructions detailed below to change the domain, or sub-domain, your HubSpot COS Blog posts are hosted on.
Navigate to Content > Content Settings.
Once in the Content Settings page, click on Domain Manager which is under Content Optimization System Tools.
Within the Domain Manager page, click Edit next to the desired listed domain (Note: if it is not present and has already been updated to point towards HubSpot's server, add it by clicking Connect Another HubSpot COS Domain).
Under where it says What do you want this domain to be used for? select Content Optimization System Tool(s) and then check Blog Posts. Once these options have been selected, click on Connect domain.
Please note that if you have an Enterprise HubSpot subscription, as well as having multiple blogs in HubSpot, and you would like to host them on different domains follow the instructions below to do so:
Go to Content > Content Settings > select Blog under Content Optimization System Options. Next, look towards the main content area of the page, and select a blog to modify.
Once you have selected a blog, scroll down to Blog Root URL in the General section and select the desired domain from the drop down. When you have selected the desired domain, click on Save changes.