Sales Assistants Really Intimidate

how to build up confidence and self esteem?
I’m 17 and i’ve just started a new job as a sales assistant and i really need to build up my confidence, every one who works there are really confident and loud and ‘cool’ and I feel intimidated, i’ve always been shy and i thought now is a good opportunity to start a new chapter.. have you got any tips on confidence and building up self esteem?
thanks (:
Your confidence will grow the longer you work there x