To create a recurring thread:
Click Start a thread on the left-side of Threads
Add in where you're posting the thread, and write your thread
Click the drop-down at the bottom right-side of the thread, next to the 'post' button:
Select Recurring Threads
Set when you want to post the thread, and when you want it to repeat
A copy of the thread will be automatically posted at the day and time you select.
You'll be able to view your recurring threads from Sent.