Before submitting your podcast to iTunes, please make sure the artwork for your podcast channel meets the following requirement.
2. After accepting Apple's terms of service, you will see Podcasts Connect option as show in the image below.
3. Input your RSS feed URL and click Validate. You might need to update your RSS feed to meet Apple's requirements.4. Click Submit and waiting for the approval from Apple Podcasts.
Go to https://podcasters.spotify.com and log in. Click GET STARTED. Then follow the instructions in the web page to submit your RSS feed.