Connecting a domain to HubSpot requires you to point that domain to your HubSpot CNAME in your DNS. Because it is not possible to point a single DNS record to multiple locations, you will need to use another subdomain to host your HubSpot content.
For example, if you are using www.domain.com to host your Wordpress site, you will not also be able to point www.domain.com to HubSpot without taking down your Wordpress site. Instead, you will need to create a subdomain, such as info.domain.com, to connect to HubSpot. Read more on connecting a subdomain to HubSpot here.