If YOU need to delete a thread that YOU posted, this can be done as follows:
Delete your thread:
Look at the top of your initial post and you will see a box/link like this:.
Click it and you should see a drop down box with an option to delete like this:
Click the option for delete thread, then click perform action button and a box will come up that looks like this:
Type your reason for deletion in the space provided and then click on the Delete Thread button.
Delete your post:
Go to the bottom right corner of your post and you will see an edit button that looks like this:.
Click it and you will see one of two things which are either;
If you see this then simply click the Delete option which will then bring up an addition to the box you are viewing that will look like this:
Click the Delete button and you are done.
The other possibility would be a screen pops up that looks like this:
If so, just choose the delete option in the top box portion like so:
Enter your reason for the deletion, click the the delete button and you are done.