Custom Sub-domain and Edit Link URL
A custom sub-domain refers to the vanity text that goes in front of "instabio.cc":
To create a custom sub-domain click the "Settings" tab then go subdomain settings:
From there, scroll down to your "Sub Domain" ,click "+Add subdomain" and enter the name would like to use. If someone else is already using it, you will need to update to new name.
You can also add subdomain on link detail page，click "Custom Link URL"
Note that the subdomain can only be used as one link URL. If you add a new type of link and want to use this subdomain, you need to fill in the shortcode behind the subdomain