Install the base plugin if not already installed. You can get the base plugin here https://www.huntbee.com/base-plugin. Follow the base plugin installation instructions to install the base plugin.
Once you have installed the base plugin, Go to Extensions > Installer
Upload SEO-Meta-Robots-x.x.x.ocmod.zip
Go to SEO Extensions > All Apps
Find SEO Index & Crawl Optimizer in the list and click the Install button.
Click on the Edit button
Make the required setup as per your preferences, and click on the Save button
Go to Extensions > Modifications. Click on the refresh modification cache button.