Changes take effect immediately or upon the next policy refresh, depending on the nature of the policy.
Once opened, navigate through the tree-like structure on the left side to find the policy you wish to edit. Policies are organized into categories. gpedit.msc
"It’s for anyone who refuses to be told 'no' by their own computer," Sarah replied. "You want to install those drivers? The system is blocking unsigned code. But policies... policies are just rules written in stone. And we have the chisel." Changes take effect immediately or upon the next