In fact, we almost never say or write the full form 'have got'. This is a feature of informal English, so it is always contracted to 'I've got' or 'He's got', for example. We can use the form 'I've got' as an alternative to 'I have' when ... 1.....you are talking about possession or something that belongs to you, 2....and you are using the present simple tense, 3....and the situation is informal or neutral. So, for example, there is no difference at all in meaning between 'I've got two sisters' and 'I have two sisters'. The meaning is the same. The only difference is that the first is more informal. - You don't use the 'got' form when the verb 'have' replaces another verb or action. For example, you say 'I have breakfast at 8 am' or 'I have a shower every morning'. You can't use 'got' in these sentences. - You don't use 'have got' in formal situations, such as a business letters or academic essays. It's fine for conversational English or informal writing, though. It's more common in British English that American English.