1: Seat the cup in the frame and use a vice to press then in
2: Get a long threaded bolt (longer than the head tube and headset) with washers of a larger diameter that the cups and with two adjustable spanners tighten until the cups are pressed in to the frame.
Four ways.......
1: Seat the cup in the frame and use a vice to press then in
2: Get a long threaded bolt (longer than the head tube and headset) with washers of a larger diameter that the cups and with two adjustable spanners tighten until the cups are pressed in to the frame.
3: Beat the cups in with a mallet
4: Take it to a bike shop