How do you open the config screen?

[xp2-882030kgz010602]

I want to know what the chance is that a mob spawns wearing a backpack, but I can't check the config because the button is grayed out.

[KuschelKaktus88]

i think u just need to go into ur config files.

go in to ur modpack folder, click on configs, search for sophisticated backpacks and edit anything u want. dont forget to save what u have edited.