Sign in your google analytics account:
Follow this Google's article instructions in order to associate a GA4 property to your preexisting Universal Analytics property:
Now, let's get your "measurement id". Click on "see your GA4 property", see image below:
When you will be on your GA4 property > Settings > Data Stream > (Click on it)> And the Measurement ID will be on the top right starting with a G-
This video also shows how to find it:
Once it is associated, send to HV support the newly created "measurement id".
HV has to finish some configurations, when you heard back from support, you may go to the GA4 property with Google Analytics and you may then see the traffic in the realtime view.