Dropdown list from different table CakePHP

I am working on a form that will allow the user to edit a certain order. I would like to be able to make a drop down list of Sales Agents that are already stored in a different table.

The foreign key is UserID (Alias for User table is SalesAgent).

This is in my view for the edit_sales_agent action: In my controller I have this:

echo $this->Form->create("Order");
echo $this->Form->input("UserID");

I thought that a drop down list should automatically be created when I do this, but a text area is created instead.

Does anyone know what to do?

Thanks!

via Chebli Mohamed