Point to note: Depending on your purchased theme, screenshots can vary. If you did any changes on any plugin files, then keep backup of them, so that you can upload those files again after updating the plugin.
You can update plugins by following below steps–
1) Login to your wp-admin.
2) Go to Plugins > Installed Plugins.
3) Now, deactivate those plugins which you want to update.
4) Delete those plugins.
5) Now, go to ‘Appearance > Radiantthemes Install Plugins’ (For some themes it's 'Appearance > Install Plugins'). Now, re-install and re-activate those plugins again and you'll get the updated plugins.