If you have acquired a Descendant, you can check it in the Inventory (I) > Descendant > Descendant List (G).
Click on the obtained Descendant and press the 'Use' button to use it.
If you have acquired a Descendant, you can check it in the Inventory (I) > Descendant > Descendant List (G).
Click on the obtained Descendant and press the 'Use' button to use it.