If the name you entered is still available, you will get a message that tells you so. Below that message you will also see other suggestions of similar names but with different TLDs e.g if you search for the .com version, you will also see suggestions for other TLDs like .co, .me, .net, .org etc. Ignore those for now and click on the Add to Cart button.
Hint: The .com or .net or .anything part of a domain name is called the Top Level Domain or TLD.
Tip: The Add to Cart button is short for Add to Shopping Cart. When making purchases and payments online, the common procedure is to first add the items you want to buy to a “shopping cart”. Think of the shopping cart as the basket (or cart) used to gather the things that you want to buy when you go to a real life supermarket.
In a real world supermarket, after adding everything that you want to buy to the cart, you can then go to the counter and pay for those items. In the same way, after adding items to an online shopping cart, you can then proceed to checkout. Checkout is the point where you are asked to enter your card details for payment.
If you are unlucky and the name you searched for has already been registered by someone else, you will see a message that says the name is not available and below that message, some suggestions of other similar names but on different TLDs. Take note of the prices quoted to the right of the available suggested names because not all domain names are of the same price, especially if they are special or popular names.
For example, in the following screenshot, notice the difference in prices between vanguardngr.me ($7.49/yr) and vanguardngr.cm ($98.00/yr)
In the event that you want to additionally register any of these other suggested names, click on the check box to the left of the name and then click on Add to Cart.