you'll need the "touch" object, the sprite with platform behavior and a solid ground where it will be placed.
on the event page put:
Condition: On any touch;
Action: Simulate Control -> Jump
To fly, set falling speed to 0 or sustain the jump for a local variable who will be counting while the touch is active and fill the sustain instance with this variable.
see the flapbird sample file inside the construct2 sample files.