YITH Donations for WooCommerce is the plugin that allows adding a form to your site through which your users can make online donations. You can show the donation form on one or more products, on the cart page, use the widget to show the donations received and much more.
When used in combination with YITH WooCommerce Subscription, it allows turning the product created by the plugin (named YITH Donations for WooCommerce) into a subscription-based product and receiving recurring donations from your customers.
After installing and activating both plugins, go to WooCommerce > Products and search for YITH Donations for WooCommerce. In the product edit page, enable the checkbox Subscription.
Now you will be able to set the subscription details like for any other subscription-based product.
For further details about YITH Donations for WooCommerce settings, please refer to the official documentation.