Pageport makes it easy to setup a custom domain. All you need to do is add the below CNAME record to your DNS. Once this is setup, you can add the custom domain in your settings.
host: page
value: cname.vercel-dns.com.
Below are the steps at the most popular domain providers.
GoDaddy
Log in to your GoDaddy account and click on "My Products".
Click on "DNS" next to the domain you want to edit.
Under "Records", click on "Add".
From the "Type" drop-down, select "CNAME".
In the "Host" field, enter "page".
In the "Points to" field, enter "cname.vercel-dns.com." (don't forget the dot at the end).
Click on "Save".
Namecheap
Log in to your Namecheap account and click on "Domain List".
Click on "Manage" next to the domain you want to edit.
Click on "Advanced DNS".
Under "Host Records", click on "Add New Record".
From the "Type" drop-down, select "CNAME".
In the "Host" field, enter "page".
In the "Value" field, enter "cname.vercel-dns.com." (don't forget the dot at the end).
Click on "Save All Changes".
Google Domains
Log in to your Google Domains account and click on "DNS".
Scroll down to the "Custom resource records" section and click on "Add".
From the "Type" drop-down, select "CNAME".
In the "Name" field, enter "page".
In the "Data" field, enter "cname.vercel-dns.com." (don't forget the dot at the end).
Click on "Save".
Hover
Log in to your Hover account and click on the domain you want to edit.
Click on "Edit" next to "DNS".
Under "Add New", select "CNAME".
In the "Alias" field, enter "page".
In the "Points to" field, enter "cname.vercel-dns.com." (don't forget the dot at the end).
Click on "Save".
Bluehost
Log in to your Bluehost account and click on "Domains".
Click on "Zone Editor" next to the domain you want to edit.
Click on "Add Record".
From the "Type" drop-down, select "CNAME".
In the "Name" field, enter "page".
In the "CNAME" field, enter "cname.vercel-dns.com." (don't forget the dot at the end).
Click on "Add Record".