Step 1: Login to the Drupal admin panel.
Step 2: Click on Administer -> Appearance and choose which theme you want to use for your website.
Step 3: You should now be able to see the theme at your Drupal Administration Area -> Appearance. Enable it and set it as default.
Step 4: The Update tab allows to viewing the outdated themes and getting the new versions.
Step 5: In the Settings section you can manage the global visualization settings for your web site. You can also overwrite them per each theme.