How Can I integrate with Linode S3 with my python backend to upload the image

Object Storage uses HTTP requests to upload, download, and list objects. You'll likely want to use either the Linode CLI or a command line tool such as s3cmd so that your program can interact with your Object Storage buckets. Exactly how to go about this will depend on your program; I do want to note that Object Storage is S3-compatible and should work with language-specific S3-compatible SDKs (software development kits) if you need to make use of those.