Step 2: First cut the top.
Now, using the bottom of the tabletop (the bottom of the metal bar under the tabletop, to be precise) as a guide, pull the fabric down slightly and cut all the way around. Follow the curves at the edges of the table closely - they need to be clearly curved, it will help with sewing later!
The pictures explain this better.
You could also lay the fabric flat on the floor, place the table on top and trace around, but that seemed like lots more work.