This is where you configure settings for the account
These settings are for all the projects, issues and users in the company/organization account.
Note that project specific settings are found in the settings tab for the project in question.
In many cases the account settings creates a palette of options that the individual projects then can choose from, in their project settings.
So, if you need to add say, an entirely new issue status to a project, and no existing status is suitable, you have to add it in account settings - Issue statuses first, for the option to be available in project settings.
For example: In issue configuration - Issue types, you configure a list of all the issue types that should exist on your account /organization. Let's say you define 5 issue types - all individual projects can then choose to use any or all of those 5 issue types in their project settings (You do need to have at least one issue type, though).
If project ABC later needs another entirely new issue type, you will have to add it in the account settings (increasing the total amount to 6 types), before it can be chosen as an issue type in project ABC.
The page contains a treepanel to the left, and a main panel to the right, where the individual settings pages load. Just click on the wanted settings page in the tree to load it.
Note: After version 5.3, the organization of the new tree page is the same as the old tabbed page, just that the tabs are now nodes in the tree.