You can easily upgrade your contest when posting it.
You may also do so while your contest is open for entries:
1. Click on your contest page's top right corner.
2. Tick the upgrades that you need. The total cost will be displayed at the bottom right part of the list.
The NDA (Non-Disclosure Agreement) and Urgent upgrades may only be applied when starting a contest.
3. Click Upgrade Contest to apply the changes.