Select the character and then in the Modify panel click on "Edit Pose"
On the Edit Pose panel select the body part that you wish to adjust and make the required changes using the Move and Rotate tools.
The fingers can be adjusted in the same way and the hand opened or closed by selecting the area in the middle of the palm and moving the mouse up or down.
Gerry
System: Win 10 Pro (21H2), Asus X99-E WS, CPU i7-5930K -3,5 GHz, 32 GB DDR4 2666-16 RAM, NVidia GTX 1080 Ti GPU - 11 GB VRAM(Driver Studio-536.99), Samsung 850 Pro 512 GB SSD, 6 TB HD storage.