Sami the linking is automatically (normally) taken care of by Access if you are using a SubForm.  If the fields are not named the same you may have to set the Link Master and Link Child fields manually.  This is all dependent on having the right Foreign Key in the associated tables.  Many-to-Many

If you don't have it as a SubForm and you are opening a different form using a button for instance, the Where condition of the form is specified with the open event. Like in the Blank Template video.

Private Sub ContactBtn_Click()

    DoCmd.OpenForm "ContactF", , , "CustomerID=" & CustomerID
    
End Sub

Check out the Contacts video again as well.

Hope that helps.