1. Click on the Settings cog in the top right hand corner of any page
2. Under 'Account Information' select 'Platform Options'
3. At the bottom you'll find the option to 'Validate automatic posts via mobile application':
4. Click 'No'
5. Don't forget to hit 'Save' in the bottom left!
From now on your auto-posts will be posted completely automatically, without any further action being required from you.