Can i just use a nail gun to add a foot to a foot and a half of lattice to a vinyl fence. I'm looking for the easiset cheapest way to add height with out planting too much as I don't want to lose space with planting.

Thank you

The lattice will need to be supported by a framework, or it will just flop over in the wind.

thank you. can screw in 2x2s? or does it need to be thicker?

Depends on the wind in your area, the width of the support rectangles and how you are fastening the top piece to the fence/posts.
Best is to sandwich the vinyl lattice between two boards around the edges either with mitered corners or vary the overlap in the corners (so the joints don't match), then it will be very secure. What are your posts like, and can you add onto the top? A picture or better description of existing fence can be helpful.