I’m using Blender 2.8, everything else is going good, although I can NOT bend the legs, how would I go by doing that?

I’m using Blender 2.8, everything else is going good, although I can NOT bend the legs, how would I go by doing that?

I’m pretty sure you have to use the move tool, go that bottom line below the torso, and drag it down. If that doesn’t work, let me know.
Thank you so much! it worked! much needed I’m new to blender