Have you already made changes to your Theme files? If so, then you would need to manually add in the latest updates to avoid overwriting any custom work you’ve done.
If you haven’t made changes to your files, then you can update by removing the old version and then upload the new version to your site. This can be done through FTP (that’s the way I do it) or through the WordPress admin.
Always backup and save everything first to be on the safe side.