To create an API Key you will need to go to https://pro.cryptapi.io/api-keys/new/. Then you must setup a name to identify easily the API Key (you can have more than one), and select the permissions.
Right now we only have the permission Address Override. The way it works is this: the "default" addresses are the ones you set up on your CryptAPI Pro admin panel, with the "override" permission it allows you to "override" the default (CryptAPI Pro settings) with the ones from the request (e.g sent by the WooCommerce plug-in). So, if for example you just want to use the addresses set on your woocommerce plugin, then check the Address Override permission, so the settings from the plug-in override the default ones from CryptAPI Pro.
Check the table for a detailed view on how this works: