How to change the size of a column from a table i have put on a Sharepoint wikipage

i am using a Sharepoint Wikipage on the page I have put a table on the page by clicking on the Table button on the ribbon. How can I change the table layout. I want to change the column width. I can go to the source of the page but I don’t know what to put. I have even a content editor on the page that connect the page with a css-file store in the folder Assets. But what ever i do change the css file or the html-page nothing works. The table doesn’t change. Does someone know how? Gr. P