Uploading your datasets to the Sentinel platform allows you to use these images in your custom model training. It is not necessary to supply your own dataset to create a custom model but will help improve the overall performance of your model if you choose to. This is especially true when your dataset includes images taken in locations you will have Sentinel devices deployed at.
When uploading a dataset folder, it is important to separate each species into its own sub-folder, as the illustration below demonstrates.