This is a very simple and effective way to do this:
-Create your player sprite, which I'll call Sprite.
-Create an empty sprite (something small like 4x4), no fill... I'll call it Camera
-Add the "Scroll To" behavior to Camera (the sprite).
-One simple event:
Every tick | Camera - Set position to
X: lerp(Camera.X, Sprite.X, 7*dt)
Y: lerp(Camera.Y, Sprite.Y, 7*dt)
You can change the "7" to whatever you want. Bigger numbers are faster, smaller are slower. 1*dt mean it would take one second for the Camera to reach the Sprite. The game window will scroll to the Camera rigidly, but the Camera will scroll smoothly to the player (making the camera move smoothly).