How To Setup WooCommerce Buy Again documentation gives you following details.
Buy Again – General Settings
In the general settings of Buy Again you can see the following settings.
Enable Module: You can enable/disable plugin functionality here.
Tab Title: Add text for tab title.
Buy Again Description: It allows you to add description text for Buy Again.
Order Details Button Label: You can add custom text for order details button label.
Description Before Products: However, admin can add text such as, all products you bought are listed below.

Front-end View For Buy Again
You can see already bought products at simple product page.

Re-Purchase Products Saved at My Account Page
You can see already bought products. You can add them again.

Re-Purchase Products Saved at My Account Orders
You can see Buy again button for already bought products. You can add them again.