Image: notice suggesting upgrading MySQL to a more recent version
At the top of the tab, you see relevant notices about upgrading your database server software. You may not see any notices here if your software is up to date.

If some or all your tables need to be upgraded to MySQL’s latest storage engine (InnoDB) and row format (Dynamic) you see a notice about that.

Current Status

Image: current status of your keys
Here you see the status of your high-performance keys.
Image: do not forget to back up your database.
Back up your WordPress site! The plugin asks you to acknowlege that you’ve done so.
Image: choose the tables for high-performance keys
Here you choose which tables you wish to get high-performance keys, and tell the plugin to do the work.

Some of your tables may have many rows in them, and the Add Keys Now operation will take time. You may prefer to add keys to those tables one at a time, especially if you use a budget hosting service.

Alternatively, you may prefer to use WP-CLI, WordPress’s command-line interface for this operation, if you have access to it. WP-CLI doesn’t time out. If you’re not sure whether you have command line access, ask your hosting service.

As an example, you can add keys to your wp_postmeta table with this command line.

wp index-mysql enable wp_postmeta

Or, to add keys to all tables you can use this command line

wp index-mysql enable --all

What keys do we add?

Please see here for details.