The selection of pre-installed widgets depends on the theme you have chosen and the plugins that have been installed.
In the left menu column, click Appearance, then Widgets. Then simply drag the widgets you want in your blog into the Sidebar on the right to activate them.
There can be more than one Sidebar, depending on the theme.
You can have a Twitter feed in your blog using a number of methods. Using the Neosential theme and the Twitter Widget Pro, the Twitter feed looks like this in the right sidebar:
The Korean blog uses the Twitter Widget Pro. To use this widget, drag it into the Sidebar, enter the Twitter username without the “@” and click Save once you finish configuring the settings according to your preferences.
If you can’t find this widget in list of Available Widgets, click Plugins from the left menu column, scroll down to find Twitter Widget Pro and click Activate. It should then be visible in the list of Available Widgets.
You can also use the plugin for Twitter Tools instead, which enables cross-posting from both the blog and Twitter:
By activating the Twitter Tools plugin, and dragging the Twitter Tools widget into your Sidebar, you will be able to write tweets directly from your blog: