There are two ways to do it - either your contact list is a string with contacts separated by a special character, or you have a separate table for this.
The problem is that SQL does not have a concept of arrays - so you can't have a row with a variable number of fields.
While you could set it up with a string:
THis very quickly becomes a PITA to manipulate or search, or worse - remove a user from your system completely.
The best approach is to create a separate table, "Contacts":
ID int - This can be an identity field.
UserID int - ID of your user
ContactID int - ID of one of his contacts
You can then fetch the list of contacts with a simple SQL statement:
SELECT ContactID FROM Contacts WHERE UserID=100
Changing the 100 to match the ID of your user.