Since the Atkins 2010 edition, the diet includes a salted broth under "Foods that must be eaten every day". From the clinic program based on Dr Atkins:

"Bouillon: 2 cups daily—as needed for sodium replenishment. Clear broth (consommé) is strongly recommended, unless you are on a sodium-restricted diet for hypertension or heart failure."

I would have one mid-morning and afternoon, the cubes are fine, and as others have said, enough plain water. You will be losing water weight to start, and the electrolytes go along with it, replacing the salt reduces the side effects.

More on other potential side effects in the first few days, and what to do about it: https://www.dietdoctor.com/low-carb#side-effects