Did you make a typo or forgot to add some information? You can edit your message anytime you want, simply by hovering your mouse cursor over the message so the three-dotted menu appears (on the right side of the message), and by selecting "edit" from the menu.

Your message will then re-appear in the message box, where you can edit it as as you like and re-send it. The old message will be replaced with the new one and an indicator that the message was edited will appear, so other people will know about changes in your message.