Department Store Job / John Lewis / Employment?

Hello, I have just left my Education...I am 18 and now need to find a full time job...To be truthful I am petrified of the prospect...It is ridiculous but I have never had a job before. I have had a two week work placement as part of my education. This was two years ago and was invaluable for me to learn how to act in a work context. I want to work in John Lewis (I guess as good as any company for a young man) or another department store. I just don't know how to apply? I have a feeling a CV is not needed...For an entry level position? Where should I go in order to get an "application form"? If so exactly what is the title for a job on the floor? Sales istant? As much information etc one could provide would be most appreciated.