To allow project administrators to make customization changes, perform the following steps:

1. Navigate to Administration > Issues > Permission schemes.
2. Click on the Permissions link for the permission scheme used by the project. If there is no permission scheme specifically for the project, create a new permission scheme by first cloning the current scheme used by clicking on the Copy link.
3. Check the Extended project administration option under the Administer Projects permission:

Once the permission scheme has the Extended project administration option enabled, administrators of projects using that permission scheme will be allowed to make changes to the project's workflows and screens.