i come out of the elevator and clear the aliens. It tells me to mark the target and proceed to the park. How do I do that. I have shot at the ship. Tried jumping off the platform. Not sure how to proceed. Please help.

Use your tactical display (default is 'B') and just look around a bit at the balcony until they say that they've got a visual.

ty--i will try that.

I opened the visor with B (default) and pressed F (default) to tag the Alien Gunship thats floating around the buildings.