Start by signing in to https://chatgpt.com/auth/login.
Next, click on your name in the bottom-left of the page, for example John Doe:
Click on "Settings" to open the popup settings modal where you will see "Data Controls" -> click "Show":
A menu will appear where you can toggle the setting "Chat History & Training" as you can see below the setting is enabled.
When you toggle this setting to disabled, new conversations won’t be used to train and improve our models. New conversations also won’t appear in the history sidebar. Please note that this setting does not sync across browsers or devices. You will have to disable history on each device. Read more on data controls.
Note: To monitor for abuse, we will retain all conversations for 30 days before permanently deleting.