Widgets are designed to replace the markup that is normally generated in your side bar. As soon as you add a widget to your side bar, all of it’s previous content will disappear and be replaced the content generated by the new widget. Think of them as mini-plugins for your sidebar
You can have any number of widgets in your sidebar although you may only be allowed to run a single instance of some widgets.
To add widgets, simply select which side bar you want to widgetize in Admin/Appearance/Widgets (you may have 1 or more side bars depending on your theme) then drag and drop the widgets onto the right-hand side of the page. Edit/configure each widget appropriately then select Save Changes.
Reverse the process to remove them.
Hope that helps.
