The WordPress posts scheduling feature is found in the Publish box on the upper right corner of the post editor page.
To schedule a post for publication, click the Edit link next to Publish Immediately. You will now see a drop-down option to select the month, date and year to publish the post, even the exact hour and minute.
For example, if you’d like to publish a post at 8 a.m. tomorrow, select tomorrow’s date, set the time for 8 a.m., and click Ok. You will now see the Schedule button has appeared.
Tip: Check that your timezone is setup correctly in Settings -> General. Check the article for more info.
Click the Schedule button and you will see that the status of this post has changed to scheduled with details of the exact date and time it will be published.
If you change your mind and want to publish a post immediately, click the Edit link next to the scheduled publish time and update the time to today’s date and the current time and the post will immediately publish.