Once you have created a Posting and it has gone "live", you are still able to make a number of changes.
Select the Posting you would like to change and select Edit.
The editing view has the same options available as when you originally created the Posting. Each section can be changed, however, services cannot be added or removed if you have already received a Proposal.
Once you have finished making your changes, click Update Posting. The Posting will be updated immediately and available to all freelancers who now meet the Posting's criteria.
Alternatively, if you are looking to close the Posting completely, and not receive any more proposals, you can hit Close Submissions. The Posting will no longer appear in your live Postings listing but can be found in the "Closed" postings tab. You can always re-open the posting within this same editing page.