The attach command allows Corrade to attach multiple (or only one) objects from inventory to their attachment points.

llInstantMessage(CORRADE,
    wasKeyValueEncode(
        [
            "command", "attach",
            "group", wasURLEscape(GROUP),
            "password", wasURLEscape(PASSWORD),
            // skull, mouth are attachment points (see documentation)
            // Helmet and Milk Bottle are object names in the inventory
            // ... You can also use UUIDs for inventory items.
            "attachments", wasListToCSV(
                [
                    "Skull", "/My Inventory/Objects/Helmet",
                    "Mouth", "/My Inventory/Fun Stuff/Milk Bottle"
                ]
            )
        ]
    )
);

The attachment parameter accepts pairs of attachment points and object in inventory. Here is a full list of attachment points:

• Please note that SecondLife terminology distinguishes between "wearables" and "attachments" where "wearables" are clothing items and body parts such as "Skirt, Shirt, Undershirt, Skin, Shape…" and "attachments" are objects. In case you are looking to wear clothing or a body part, then please use the wear command.
• If you are looking to change the entire appearance of the bot, as in, changing an outfit, then please use the changeappearance command.