Here, 'shape' is a verb. It tells you to move your lips, tongue, cheeks etc. into a certain position (probably to say a vowel). 'Properly' is an adverb describing 'shape'. It means the same as 'correctly'.

What is the context? Usually this would be used to describe how you move and position your lips. When I say "O" my lips are shaped like a circle. When I pronounce "t" they are flat and don't move much.