Stylish Price List automatically centers itself. If the price list is not showing up centred on your page, then you need to figure out why.

It could be:
1. If you're using a page builder, then see if the row has a centring option. Read your page builders manual.
2. Try switching themes and see if it fixes the problem.
3. Make sure the parent div (that SPL rest inside) is set to display: inline-block and text-align: center.

If you're still having issues, you need to contact an HTML/CSS developer.