In your theme, you have a file called sidebar.php. You can edit this by going into Admin-Presentation-Theme editor. Then look down the righthand side for all the files that make up the theme. Sidebar is one of them. If you look at your blog, each of the bold headings in the sidebar will be define a section in the sidebar. It's hard to tell exactly what you'll see when you go into the editor because each theme is different.
To add a slideshow and a clock, you'll have to look for a plugin. This will give you the functionality of a slideshow and a clock. Then you will have to add some code in the sidebar.php file to make it display in your sidebar.
I hope I explained that simply.