A coin cell? A CR2032 at 3V just barely makes the mimimum on the recommended operating conditions. If you really want to try, then you could hook up the CR2032 directly to 3.3V. A CR2032 is rated at about 225mAh so you might get up to 10 hours on it without any peripherals attached but if the battery gets weak and voltage dips, you are risking a lot. You might dip under 3V very fast depending on the current draw especially since you are below 3.3v. You can’t yet use low power modes so this is strictly an on or off proposition. I would rather suggest a small LiPo using the connector. You can get some fairly cheap LiPo batts on Digikey.
As the data sheet states, do not use 3.3 V pin for powering the boron. It just won’t work. Use a lithium ion battery.