To buy a domain name from Domain.com, you should do the following steps:
Search
Type in the domain name you would like to buy and click on Search Domain.

Added To Cart
Once the domain is verified to be available, it is added to the shopping cart. Click Continue.

Proceed To Billing
Verify your order and proceed to the billing section.

Billing & Payment
Type in the credentials, verify the order, and click the Purchase Now button.

Register
Register a new account or log in at Domain.com.
Connect
You are done. Click the DNS tab to connect a domain name to your Nicepage site.