Somebody has to buy the land first before you can sell it.
But because nobody owns the moon (yet), you are free to claim your land, just like our ancestors did in the past.
So hereby I claim 1:53:21.38 N 3:44:54.81 E to be my property.
I will be setting up a palisade next week to show my properties boundries. I hope the gasprice won't go up next week or else I wouldn't have enough money to fund this and have to sell my land for $1,000,000,000,000