Welcome to the Forum! The first thing you need to do is contact a supplier and ask for their approval to dropship their items online. You will then setup a dropshipper account with them and they'd provide you with their product catalog for you to list items for sale. Each time you make a sale, you login to your drop shipper's account and order the items on your buyer's behalf. Your supplier will then send the items direct to your buyer's address without any price information because you have a dropshipping account with them. You will be the one to send the invoice direct to your buyer online, and not your dropship supplier.
Hope this clarifies.