I suppose you use WooCommerce Custom Tab v1.0.7. In this version the plugin must be enabled in “Settings” / “WooCommerce Custom Tab” menu of the Admin area. Check in the enable plugin checkbox. (This checkbox is removed since v1.0.8 version.)
After enabling the plugin, please chose “Product Tabs” menu in the WP Admin area, and add new tab types.
Then go to the edit pages of your WooCommerce products, where you will find editor fields for all defined tab types. Here you can enter the content of your tab pages of the specific product.
We hope, you can add your tab pages according to this method.
If you have more question, please do not hesitate to contact us.