The Post Settings is a section found in your Profile Settings page, under the Posts tab. There you will find the Posting Frequency setting.
This is used to set up your Queued posts one after another. The Posting Frequency Interval dictates how long after the latest Published or Queued post should the next one be queued up.
There is a bit of randomness to the Frequency done by adding or subtracting from the value a number of minutes. So, using a frequency of 30 minutes, your first Queue will be set to Publish at a random time, around 30 minutes (give or take a couple of minutes) from the last post you Published or Queued.