When working with your Enterprise advocate to upgrade to Enterprise, they'll need two pieces of data to finalize that upgrade:
The URL of the initial Workspace you want to upgrade
The Enterprise admin username
You'll be able to add more Workspaces later on (Upgrading an Enterprise Workspace) and set more admins (Enterprise admin dashboard), but you need to start with an initial Workspace and an initial admin. The admin you pick here MUST be an admin on that initial Workspace.
Typically, you are the one requesting the upgrade, and will be designating yourself as the admin, so these instructions assume you are that person in question and have access to the Workspace that will be upgraded.
If that doesn't describe you, and you need help locating this, let us know! https://trello.com/contact
How to find the Workspace URL
Go to https://trello.com/my/activity, and you'll find a list of your available Workspaces:
Click on the one that you will upgrade, and that Workspace page will load:
The URL to supply your Enterprise Advocate is in your browser's address bar! You can also right-click on the Workspace name from the listing at https://trello.com/my/activity and choose "Copy Link."
How to find the admin username
Go to https://trello.com/me and you'll find your Trello @username listed at the top, next to your name: