Widgets can be added from the admin area.
Login to the admin ‘Admin Page’, in the left column click on:
Appearance > Widgets
This will bring up a screen with the available widgets, and a list of widgetized area’s (sidebars) in the right column.
Click on one of the widgetized area’s headers (right column) and it will show a dropdown content area.
Drag any widget fron the main area to the widgetized area.
Notes:
Most themes have a pre-populated sidebar, when you add widgets these will not show and you will need to drag them across.
Some theme authors add extra widgetized areas and build in their own widgets, these are often selected from a special menu or Appearance > Theme Options.
You will find lots of short video’s on YouTube or a Google Search will also help.
HTH
David