How can I change width of Table Cell in "SB Admin" Template?

When I change witdth in Appereance/Layout it doesn’t do anything:

You can’t change the width on the table cell in the table body, try to change the width in the table header on the cell that says Picture, maybe replace the text Picture with an icon of an image

or try with this css

table {
  table-layout: fixed;
  vertical-align: middle;

th:first-of-type {
  width: 1rem;

Also can’t chnage it in table header.

I haven’t tired the css. I have abandoned trying to change this template. Seems to easier to start with blank page.