Can I register more than one domain name at the same time?

In the upper menu press on "Domains", then on "Bulk register domain":

You will see the field where you can enter the domain names with the desired TLD:

After pressing on "Check domains", the list of your domain names will appear in front of you.

Add to a cart what you need (or press on "Add all") and then press on "Proceed to Cart" for a payment. A soon as the invoice(s) will be settled, in a couple of minutes your new domain names will appear in your list of the domain names.

See also How can I pay for my domain names and other associated services?