If you want to delete a scheduled post, follow these steps:
Click Schedule Posts on the Social Media Home, os Publishing on the left side menu.
Click the eye icon to see all scheduled posts from all your accounts, or click the eye icon next to the account you want to see scheduled posts.
Find the post you want to delete on your view (Calendar, List, Feed or Grid. On Calendar View you can scroll or find by date, and on the other view types you can filter by all, past or upcoming. Select upcoming to find a scheduled post).
Click the '...' icon on the top right corner of the post, then click Delete.
Confirm by clicking Delete on the pop-up window.