Just go to Products & Services, click on the “Check Domain Name”
or
http://www.kkboss.com/products-services/check-domain-name

type in the domain name (e.g. mynewco.com) and then click on the “Submit” button.

If the domain name is available, it will say something like:

No match for domain "MYNEWCO.COM".

Meaning, you can register this domain name.

If it show a lot of information about the domain, such as the registered owner,
then this domain is not available.

Just continue to search until you found the domain name you want.