How does the "Correct Answer"-button works? Should I use it?
You simply click on the "Correct Answer" button contained in whichever reply you found to be the most helpful.
It is not mandatory to use the button, but it does help others to quickly find the correct answer when searching for a solution to a similar problem.
You might want to wait to see if other soultions are offered before clicking the button, however the selection can be changed if a better solution is given at a later date.