adding/editing sidebar

Hello everyone!

The page I’m referring to is https://www.photocs.net/blog/

As you can see, I’ve edited a standard theme to match the rest of my website, the starting point being the theme Default 1.7.2 by Michael Heilemann.

As you can also see, the current setup is one without a sidebar, however I’d like to add one but do not know how to begin adding one. Of course I’ve tried doing it by adding widgets to the sidebar within my wordpress dashboard thing, but that doesn’t seem to do anything.

I created my whole website without any prior knowledge of anything like CSS or the like, so if you look at the code it may be messy. I also understand that I should be giving a bit more information, etc, about what I’ve tired but I’m just not sure what else to include.

I hope someone can help!