Can I have olives? Are they classed as fats or carbs?

Yes, you can have olives at any stage of the diet.

Olives are a fat product (as is olive oil). There is barely a trace of carbohydrate in olives. So they can be eaten with fat meals (steak, cheese salad, omelettes, fish etc), but don’t have them in large quantities with carb meals (rice, pasta ...