Log in to your account. Go to the tree you want to export.
At the top left side of the tree you’ll see a button with the name of the tree and a down arrow. (Next to the name of the tree). Click once on the down arrow and you’ll see the menu item “tree settings.” Click on tree settings.
On the bottom right you will see a green button that says “Export Tree.” Click that button.
After processing, the button will change to say “Download your gedcom file.” Click on that button.
Save the file to a place on your computer where you will remember the location. (The desktop is a good place to put it if you are unsure.)