One way the metadata is established is when you save the asset to your library, it will establish a category file type for each item saved based on the preset type it was saved as.

Remember when saving a Wearable preset, that this preset type will draw on already saved data assets for items to re-add the items to a selected figure. The best use of a wearable preset is to load a complete outfit onto your figure from a variety of products and then save as a wearable preset to reload the collection of assets with a single click again later. You can also include morph shaping, Pose, and material presets to the base figure of the wearable. Wearable preset will not save any actual data assets when they are saved as it draws on preexisting ones for each item.

Most clothing items should be saved as File/SaveAs/Support Asset/Figure Prop Asset...

Pick a name and location and fill out the dialogue box with the item details before saving. Take note of the Product Name and Author Name as this indicates where the associated data files will be stored. Generally in your content library data folder: Data/AuthorName/ProductName These are the data assets your currently missing.

If you want to change the metadata type later for a saved file you can locate the folder of the item in the Content Library Tab and select the Content DB Editor from the drop down at the top of the tab. This will show the associated metadata for the folder contents, the Category section is what defines the tag and type and you can change it to what you prefer and it will change the Metadata file type for the file. But it will not change the actual file in anyway. So you could tell DS that a Pose Preset is a Material Preset and it would show it as Material Preset. But the preset would fail when applied unless used like a pose preset.

Also Metadata data is stored locally for each product in the Runtime/Support folder which is made up generally of three files. Productname.dsx, Productname.dsa, Productname.jpg. If you want to transfer any metadata you have made you would need to include these into your distributed content. But I would suggest doing as much research into metadata as possible first, as it is something that's pretty easy to mess up at times and is quite an involved process.