Go to the specific campaign you are trying to duplicate by clicking the three dots located at the right side of your campaign dashboard and select Duplicate.
You’ll be redirected to set up again from your chosen campaign type with the same sequence and messages but you can change or add another sequence before you publish it.
Please note that you can only duplicate the same type of campaign. E.g if you have created it using LinkedIn Search once you duplicate it will be the same type of campaign but the messages are the same with your selected duplicated campaign.
Also you can only duplicate CSV campaign and LinkedIn Search campaign.