1. Download a fresh copy of WPLMS installable WordPress theme file from your themeforest account.
2. Login to your server via ftp or Cpanel.
3. Go to wp-content/themes folder of your wordpress setup.
4. Cpanel : Upload wplms.zip. Remove the existing wplms folder and unzip the wplms.zip file
OR
4. FTP : Unzip the wplms.zip file ondesktop and replace the existing wplms folder.
Your theme is updated.