If you have an existing popup or bar, simply go to the "Manage" Tab within your Hello Bar account dashboard to look for the popup you want to change. On the right side, click on the gear icon to reveal the drop-down menu and then select "Edit" to open your popup in edit mode, where you can then make changes to your text copy or change any aspect of your popup. 

If you want to create a new popup from scratch, simply click on the green "Create New Popup" button found on the left hand side your dashboard and proceed in creating one from scratch.

Once you have decided you want your popup to appear only when the user starts to leave your webpage, simply configure the section "When does it display?" located in the popup editor's "Settings" Tab shown below...

Make sure to select "Exit intent (user begins to leave your site)" as shown above.

Once you are happy with the edits you've made, please make sure to click "Publish" before exiting the popup editor to push the new version of your popup to your live site. 

Note that clearing your browser's cache and cookies may be needed before you can view the edited popup on your actual site.