Trigger to update a column in a new record to CURRENT_TIMESTAMP as it is inserted

Ok, so I'm trying to update a column to a CURRENT_TIMESTAMP in a specific record whenever the record is originally inserted. This is what I've got but otherwise I am lost. CREATE TRIGGER dbo.TrgUpnInsert ON [CNLH Security Authentication].dbo.DateTimestamp AFTER INSERT, INSERT INTO [CNLH Security Authentication].dbo.EntranceInformation (DateTimestamp) Values (CURRENT_TIMESTAMP);