Welcome!
A scene larger than the resolution you set in the games properties should scroll by default when the playable character reaches the edge. No need to change anything.
In the scene properties you can also check the box "scroll scene if the cursor is at the screen edge". The default setting is that the scene is centered on the character. So when you move the scene by moving the cursor to the edge, the scene will return to the character as soon as you move the cursor again. If you don't want this to happen, you need to clear the centering on the character. There is an action part for this, called "center scene on character permanently" with a checkbox to clear the centering.
So that said I'm not sure what you did to scroll the scene. Do you have a first-person-game and used a script for scrolling?
Then it is easy to add easing. If you are using the to() function, just add the easing at the end, like in this example.
The first line is to clear the centering of the character, but that can be done with an action part as well.
The 3000 is the time taken for scrollin in ms. The scene will scroll to the x positon of 1500 and the y position is kept the same.
game.ScrollCenterCharacter = false
game:to(3000, { ScrollPosition = {x = 1500, y = game.ScrollPosition.y} }, easeQuintOut)