Allow woocommerce customers to redeem coupon/vouchers without selecting the products and applying the coupon. Use short code [ws_redeem_voucher_form]
Use the WordPress Add New plugin to upload and install the plugin.
Use the shortcode [ws_redeem_voucher_form] in your post or pages.
NB: You can also unzip the file and upload the entire folder to your wordpress plugin folder. In the list of plugin you show now see the WS Redeem Voucher plugin. Click to install and activate.