a foreign key column is just a column that you add to the second table to create the relation ship to the users table.
Your users table will have a primary key column, this is a unique identifier for the user.
it will be set to a numeric value and will be controlled by the database using an automatically incrementing value.
This is the users id.
in the image table, you need a numeric column that will store the users id to create the relation of image to user.
if you are using Security assist, take a look at the recordset on the profile page, this will demonstrate how to filer the recordset on the user id session variable.