This highly depends on your backend and infrastructure and how you want to store the image files, for instance, in S3 or Google Cloud Storage or you have something on your own. We do not provide any storage solution. Please take a look at how to store assets in the documentation of these vendors or talk with your backend team.
Once you have stored the assets somewhere in your infrastructure, you need to implement an asset source that is querying these data and returning the assets. The CE.SDK needs a valid URI where it can fetch these assets. It does not return the actual blobs but just references.
Please take a look here and here on how to implement these asset sources and then at this documentation on how to show an asset source in our UI.