It depends on what you want to say. I have an ice cream (if I was holding an ice cream in my hand, I would say this) I get (an) ice cream when we go to the beach I eat (an) ice cream every day for dessert In most cases use of the 'an' is optional.

The word 'have' can mean two different things: 1. If you say 'I have some ice cream in the fridge at home' or 'They have nice ice creams in that shop' or 'Do you have any ice cream?', you are using the verb 'have' in its literal sense of to 'possess.' 2. As you know 'have' can also act as a substitute for other everyday verbs, such as 'eat' or 'drink'. When used in this way, 'have' has exactly the same meaning as 'eat'. For example: Let's have an ice cream = Let's eat an ice cream I always have ice cream for dessert = I always eat ice cream for dessert Native speakers usually use the 'have' form. The 'eat' sentences are correct, but we don't often say them. They sound a little unnatural to us. It seems unnecessary to use to say 'eat', as it is obvious that this is what we do with the ice cream. What else can you do with an ice cream? It's the same as 'have dinner/breakfast etc' or have a beer or a coffee or a glass of wine. 'Get an ice cream' has a different meaning. The verb to 'get' means to obtain. So if you say 'I'm going to get an ice cream' means that I'm going to go to the fridge and take one, or I'm going to go to the shop and buy one. When you have got your ice cream from the fridge or the shop (or more clearly, in American English - when you've gotten your ice cream) , then you can eat it. I hope that all makes sense.

It depends; if you want to buy/order.. you use get. I'll get an ice cream with that.