First you need the following item, remember that character from any class can use it. Enhanced Merchant Envelope (3 d.) Merchant Guild document that allows you to hire an experienced seller. You can explore the game world or even quit the game - the hired salesperson will do all the work for you! - Allows to sell up to 4 items. - The store is open for the certificate validity period. - There is a commission of 5% of the value of the product for the sale of goods that are more expensive than 10.000.000 zeny. - After the transaction and in case of the closure of the store, items and zeny are recevied via RodEx - Only 1 store can be installed from one account.
You can find'em in "Win Win Machine", those are occasionally active for a week via launcher... OR someone sells'em to you in a Shop, since they're not Account Bound.