access bitmap resolution dialog

I am trying to set the resolution, but the menu option i grayed out.

It worked once after half an hour trial and error, but now I cannot reproduce it.

I am in a drawing where line is vector and color is bitmap.
I click the particular cell in the timeline and am in the bitmap layer.
Then I try to select from drwaing menu, but menu item is grayed out.

What are the exact steps to access this menu item?

Thank you.

Hi, There,
Please refer to the User Guide:
http://docs.toonboom.com/help/harmony-11/workflow-network/#_CORE/_Workflow/004_CharacterDesign/Drawing_Tools/040_H2_Drawing_with_Bitmap_Brushes.html
How to change the bitmap resolution at the drawing level
and
How to change the bitmap layer resolution at the scene level