Microvellum Community

how to change an existing name on the sheet stock library

Hello Microvellum world,
I am trying to rename an existing material name on the sheet stock library, (following a training article instructions) but the edit option is "grayed" out on my window. I've attached a screen shot of the article and a screen shot on my window. 
PS: i was hoping to edit the existing name and avoid copying the material to the project level.
all i want to achieve is remove the "PB" on the material name