Click on the Settings menu link under Subscriptions on the WordPress admin menu to access plugin settings.
Settings page has the following tabs: General, Capabilities, Flow and Gateways.
Add To Cart button label - the text to replace "add to cart" default label.
Enable multi-product subscriptions - enabling the multi-product mode of creating the subscriptions. Read more in separate article about this.
Cheapest product is one with - indicates how to display the cheapest product in variation.
Product sale price applies to - discounted price could be preserved for all renewal orders or only initial order.
Charge shipping for renewal orders - whether or not to charge shipping on renewal orders.
Subscription limit - active subscriptions could be limited for one customer (one per product or one per site).
Trial limit -similarly free trial usage could be limited too.
Capabilities settings tab has the following options:
Allow customers to cancel subscriptions - whether customers should be allowed to manually cancel their subscriptions from the My Account page.
Allow customers to pause subscriptions - whether customers should be allowed to manually pause and resume their subscriptions from the My Account page.
Moving to the Flow tab - a subscription flow illustration is displayed at the very top of the page as a reference:
This is followed by several sections of settings fields.
Generate renewal orders - how many days prior to Payment Due date renewal orders must be generated. Make sure this period is shorter than any billing cycle and trial length. Setting this to 0 will generate renewal order just before Payment Due action is performed.
Enable payment reminders - whether to send payment reminders to users or not.
Send reminders before - how many days before next action (payment due, suspension, cancellation) should reminders be sent (separate multiple values by comma).
Enable overdue period - whether non-payment on a payment due date should be followed by a grace (overdue) period or not.
Overdue period length - how many days should subscription be kept in overdue state before it is suspended or cancelled.
Enable suspensions - whether non-payment on a payment due date (or after overdue period ends, if any) should be followed by a suspension period or not.
Suspension period length - how many days should subscription be kept suspended before it is cancelled.
Gateways tab has options to activate built-in payment gateways:
Right from that page you can go to WooCommerce's checkout settings pages of each gateway. Note that deprecated gateway will only be seen to customers who used it before. Read more on how to setup gateways settings in general, and also specifically about PayPal Express Checkout setup.