Remove categories in sidebar

With so little information, no way to offer much help – please read:

http://codex.wordpress.org/Forum_Welcome#Include_as_much_information_as_possible

You coded the theme from scratch? How is the sidebar called? Remove it from there and change the CSS for the page would generally be how to do that.

theme I created

very good – then you will know what to remove;

generally, the sidebar is probably called with get_sidebar() in the templates; remove this code, and adjust the css to stretch the content over the available space.

http://codex.wordpress.org/Theme_Development