This article explains how to make changes to a Contract Request once it has been submitted.

Generally, contract requests are only editable when they are in Draft status.  Once you validate and submit, the request is locked.  This is to prevent changes from being made after an approver has approved.

However, sometimes details change after submitting for approval or when a request is pending OCM review.  In this scenario, you can withdraw the request, make changes and then re-submit.

To withdraw a request that is in Pending or Submitted status, go to to the contract request, go to the last screen "Review & Submit".  Find a silver button labeled "Withdraw".  This will change your request back to draft status.  You can then make changes and re-submit.

Any approvals that have been received will be cleared out, and so you will have to have re-approval based on the changes.  No other data will be lost in the request.