You can do this one of two ways.
First is giving the character a drag-and-drop behavior.
Second is by using LERP.
Createa Global Var: BIND_SPD = 0.2
On is touching screen | set character X to lerp(character.x, touch.x, BIND_SPD)
On is touching character. | set character y to lerp(character.y, touch.y, BIND_SPD)
0.2 is a good scroll speed but adjust it with ranges 0.05-0.9 and see what works best for you.