First, make sure what you’re going to see on the other end is really worth improved quality. If it’s Uncle Billy, you might want to keep it fuzzy? =/

But if you’re sure, then click Messenger and select "My Webcam."

Click Messenger again, and this time, select Preferences.

Click Webcam, then at the top, click Camera Settings. You can also use the slider under “Broadcast my webcam with” to choose your balance between faster-speed transmission vs. higher-quality image.

When you’re done, click Apply, then OK at the bottom of the window.

Note: Accessing Preferences without first clicking “My webcam” will gray out the camera settings & selection button.