To create servers on Vultr, you can create a Cluster and choose Vultr as the hosting provider.
You'll be asked to login to your Vultr account and copy the API key into Hatchbox.
Make sure to allow access to allow Hatchbox to access your Vultr account. You can either allow all IPv4 & IPv6 or allow the specific IP addresses. These are subject to change, so you may need to update the allowed list of IPs on Vultr if these change.
Next, Give the API key a name (to help you differentiate between Vultr accounts) and hit save.
You're now able to create servers on Vultr!