Application Letter For Sale Position First Job Interview For Retail Sales Position?

First job interview for retail sales position? - application letter for sale position

Recently, I received a call for an interview for the position of assistant in a retail sports store. I have never had a job before, was not an interview and I'm not sure what I need. I read a lot about dress themselves, be confident, smile, eye contact and everything, but I am still very nervous.
One of the things thats has me worried is to bring something to. Do I need a resume? What Refence, I have letters from people telling me as a reference on my application?
and there is more information than I think I need to know really appreciate it.