Claiming your property is a fairly easy and quick process. When you claim your property, it automatically protects the entire area from sky to the lowest block you have placed. That means your sky base and your basement are 100 percent safe from griefers.
When you first start out on the server, you are given a limited amount of claim blocks; however, you earn more by playing. You get 100 per hour of un-afk play time. You can check your progress with this amount with /claimlist. You can also get more by donating or voting.

Craft a wooden shovel. This will be the tool you will use for this process.

Right click opposite corners of the area you want to protect. When you first mark 1 corner, it will change over to a diamond block. This will tell you that you have started the process. When you mark your second corner, it will then outline the claimed area with glowstone and gold blocks.

To check if you have appropriately claimed everything, grab a stick and right click the area. It will tell you what you have claimed with the glonestone and gold blocks as well as tell you the dimensions of the claim.