Deleting: Archives, Categories, Recent Comments,

if you are referring to the sidebar area,
there should be an easy way of replacing them with some widgets of your choice:
dashboard – appearance – widgets; drag some of the widgets into the (empty) widget area(s) on the right.

to remove the sidebar totally, you will need to edit some of the theme files and adapt the css;

in this case, please post the name and download link of your theme, and ideally post a link to your site.