It seems you're looking to connect an email to the Conversations inbox in HubSpot. Just to clarify, is this a team email that multiple users in the account should have access to?
It'd be great if you could clarify what type of email you're trying to connect and who should have access to it in HubSpot, as there are 2 different ways in which you can connect your inbox with HubSpot:
If you'd like to connect a team email / shared email address that multiple users have access to and use to communicate with customers, connecting this email with the tool Conversations is indeed the best solution. Please note that if an email is connected to the Conversations inbox, all incoming emails will get forwarded to HubSpot and will be visible to all users who have access to that Conversations inbox, even the emails that you've marked as private in your email client. If this is okay, please check which provider your inbox is hosted with, as there are native integrations with Office 365 or Google available. We only recommend forwarding to a hosted email address (which is the process you've shared in your screenshot above), if your inbox is hosted with a different provider. Customizing the forwarding address in this case is optional and you can also use the suggested default forwarding address, as this is not the "From"-address your customers will see. It'll only be saved in your email client's settings, which you'll do in the next step if you follow the guide (instruction article here).
If some of the emails that arrive to that email address should remain private, I'd recommend connecting the email address as a personal email in Settings > General > Email. This will allow you to send 1:1 emails from HubSpot and also automatically log selected email replies with the help of the HubSpot Sales email extension or add-in.
I hope this helps!
If you'll encounter any problems with the inbox connection that you'll choose, I'd recommend connecting with HubSpot Technical Support, as Support is included in your subscription and they will be able to provide real-time assistance with this matter.