Simply follow the guide at https://docs.roqqett.com/docs/woocommerce-plugin.
Please note that this version does not come with support for Roqqett Checkout with Dynamic Shipping.
When using Roqqett Checkout, the plugin does not yet support the new default "blocks" for the checkout page, so it must be reverted to "classic cart" mode. See the Woo article on how to do this.
This plugin now requires the Woo Legacy REST API plugin to function properly.