The following information is from the LC Homepage, pasted here for your convenience. The pics will be changed later to reflect the new format, but the principles still remain the same to access the Item Mall.
The Item Mall in Last Chaos is an in-game shop which you can access at any time during your gameplay. Offered in the mall are items to enhance your gameplay experience, as well as help you achieve the competitive edge needed to go head to head with "Power Gamers". Before you can use the item mall in Last Chaos you must first fill up your Aeria Points by purchasing them at the Recharge Center. After you have fully Charged your Aeria Points, start Last Chaos. Once in the game, the Item Mall can be accessed at any time during normal gameplay by pressing the Item Mall Hotkey located at the far right on your Hot Key bar. The items available in the mall are categorized as below. You can click on the category to see the complete list of available items.
Items that cover your basic needs in the game such as Harvesting Production Materials and Upgrading Items.
Single use items: consumed after their use
This category contains potions: particularly valuable items for game play. Such potions can restore HP, MP, boost your attack and defense, or your XP gain.
The special contains items that would make your character stands out in the crowd such as Costumes and Covers for your Avatar and Weapons.
Packages of related items that can be purchased together at a discounted price.
Accessing Item Mall
Inside the Item Mall
At the top of the Item Mall you will find 4 tabs. The New Item tab (Default when opening the item mall), All Items tab, Records tab, and the Help tab.
New Items Tab
After you click on the Item Mall Hotkey, you will see the New Items section of the item mall. This is the default tab showing when you first open the Item Mall. Here you can sort Items by what is the newest and what is the most popular. On the right side of the Item Mall you will see your Shopping Cart. This will show you what items you currently have selected for purchasing, and the total it will cost to purchase all selected items. Below your shopping card you will find your current Cash Balance. That is the amount of Aeria Points that have been converted to be used in Last Chaos.
All Items Tab
Clicking on this tab will display all of the items currently for sale in the Item Mall, sorted by type. Clicking on one of the buttons to the left (Consumables, Basic Items, Potions, Abata, Weapons, Armor, and Packages) will display all items currently available in that category. Clicking on an item will give you the price, as well as a description of the item. Just double click an item or drag it to your Shopping Cart to add to your current list of items to purchase.
Records Tab
Purchased Items is the default section shown when you first open the Records tab. This will show you all of the items you have purchased and provides a convenient way to transfer the items into your characters inventory. The Transactions section will display all of your purchases ever made in the item mall. You can sort by Year, Month and Date of the transactions.
Help Tab
This section reiterates all of the information found in these pages.