i'm guessing you already added an human from the anotomy
To change the position of tha hands, select the cubes and a gizmo for position/rotation will appear. The spheres are for elbows. The same thing for feet and knees. For the other parts, just click on the specific parts and the same gizmo should appear. The gizmo's are for pozition, rotation ans scale. In the up left corner you can change what type of transformation you want and in what plane (local or global)
To change more granular parts, there is a pose tab. There you have more options for fingers, face/eyes and toes. If you want a specific hand gesture / face you will have to make them yourself. I didn't add any predefined sets
If you want a different body type, you can also change it in the "body" type. There I do have some predefined stuff, but here as well you'll have to make them yourself. But at least you can save them for future use