By installing the LiteSpeed Cache plugin, you can take advantage of our super-fast server side cache for your WordPress website.
First of all, disable any other page caches as these could interfere with LiteSpeed Cache.
Then you need to download the plugin from here.
now, login to the OpenCart admin console.
Go to Extensions followed by Installer
Click Upload and then select the file you have just downloaded.
Once uploaded, navigate to Extensions and select Modules from Filter. Scroll down until you find LiteSpeed Cache and install the plugin.