First you need to set up your collection in your store. Shown is a Shopify store but this works in all platforms.
Once you have your tags set up you can now add any of these tags in Dropified to your imported product and the product will be placed in the correct category.
If you only want the product in one category you can select only one tag, but if you would like the product in more than one category then you can select as many tags as makes sense.
You can add tags from other collections as well if you would like the product in other categories like "Featured Categories".
How To Add The Tags In Dropified
The easiest way to add the tags is when you import the product with the Chrome extension. When you have the product open in the extension then click the More Options button and you will see the following screen:
The other way to add products to collections is in the Edit page in Dropified.