Well if your template container element is not fit to your needs then there is a time to calculate a little bit. It can be the most precise solution in some case.
For example: You have a 1000px wide container and your slider is only 600px but you would like to align the slider to the center of the container. First of all you have to subtract these two numbers. (1000-600=400) The result, so the empty space is 400px, now you have to divide it to two part, because you need margin from left and right too. The final result is 200px. Okay now you have to write these two values into the right place. Please go into the Smart Slider 2 -> choose your slider -> click on the edit slider button and the fourth parameter is the margin, so just write the values. (you can find a small toggle after the margin value where you can switch the percent to pixel value)