My question is about the password I bought 2 days ago Macbook Air laptop computer when I set up I type to the box App I and password was ok but when i try to make open iCloud my apple Id and password it is not working

To Whom It May Concern,

I bought the Macbook Air 2 days ago when I had to set up or registrasion with the laptop my App ID and password was ok but with ICloud it is not working I went to back to the store Lady told me delete password now I have a to different password when I open computer it is different when I go to the iTunes also different and I got the massage I don't have any Apple ID and password Everything is weird what can I do I love this computer please let me know Sincerely Katalin