C# MVC populating drop down value from DB

C# MVC populating drop down value from DB

I am struggling to understand MVC. I have created couple of pages that
work. Now I created a new page which has a dropdownlist which needs to
populate from a table called accounts(coloumn is called accountNumber)
However there is a relationship with that table and table called
customer(customerid).
In essence the user whose logged in has a customerid.
what is the easiest way of doing this? when I enter
@Html.DropDownListFor(u => u.
none of tables I need pop up