In this case, your custom domain will look like
https://form.yourbusiness.com.
Log in to your Hostinger dashboard
Go to Domains -> Domain portfolio
Click on Manage next to the domain
Go to DNS/Nameservers -> DNS record
Under the Manage DNS records section, select CNAME as the Type
Fill the Name, Target and TTL fields as seen on the custom domain setting page on NeetoForm.
Click on the Add Record button
For more information, refer to the official documentation