The CATEGORY MAPPING page is for mapping WooCommerce categories to Ozon categories. Admin has to select the WooCommerce categories by selecting the checkbox and choose the Ozon category from the list in which they want to list WooCommerce products on Ozon.

In the top menu bar, the store owners will hit the Category Mapping section which appears as mentioned in the screenshot:

Choose the WooCommerce category which you want to map by selecting the checkbox. And then choose the Ozon category from the list displayed in the dropdown box and click on the Save button.