From the My Loads screen, locate the load you wish to update.  Click the 3 dots at the end of the load and select a different status, or choose Remove from List if you no longer wish to save it.

Note:  Keeping the status of your loads up-to-date will allow you to keep track of which loads you've already called and and the ones that you have booked.  Loads that you book can be stored here indefinitely, allowing you to review the details (eg. rate, weight, etc) if the need ever arises.