You can trim your moustache to the same length as your beard, or leave it slightly longer to make it stand out more. For a nice, clean lipline, close your mouth and smile. Keep your moustache clean and trim the bottom (without the trimmer comb) to create a 1 mm clear line above your lips (optional).
Knowing how to trim your beard properly is something of a life skill, and will serve you well. Keep it in line, and it’ll be an asset to your face.