Navigate over to the contract management section.
This will bring up a list of all the contracts divided by CSI Division. For example the first group of contracts might look like this:
Let's say Test Company 3 was supposed to be a prime. Click the make prime link for Test Company 3. This will bring up a make a sub a prime dialog. Click Mark as Prime.
When the page reloads Test Company 3 will now be a prime contract.
When a contract goes from being a sub to a prime it still has all the previous prime contract's attributes. So you need to you can edit the now prime contract. To learn how to do that see the How to edit a contract article.