You can ask for a free revision within a period of time specified by our revision policy (during the first 48 hours after deadline expiration for orders below 20 pages and 30 days for orders longer than 20 pages).
After the order is delivered to you, access your account, go to the "Completed orders" section and choose the "Revision request" option.
To get the paper revised properly, you have to provide clear revision instructions and set a new deadline.