Same resolution for all computers

Hi! Im wondering how to get the same resolution for all computers for a wordpress site? My site is https://www.saniaclaus.se and my resolution is 1366 x 768. Id like it to look the same for all or the most common resolutions (1028 x ? and up). I read on this website that its possible https://www.techieblogger.com/2009/08/screen-resolution-javascript-css.html

but it didnt work when i tried because i dont have an “outer wrapper” and “content wrapper”, only one WRAPPER. + nu single entry, only one for post. entry (all in my stylesheet of the theme in wp-content). Also, when i edited this, added margin: auto; i did in the direct file (stylesheet in the themes folder in the specific theme) and not through the appearance option in the wordpress dashboard and then the editor page.

When i edited, the site became centered, though i want it to be aligned to the left as it is now.

Hope i explained clearly and someone can help me out =) thnx!