Direct Instruction of How To Implement a MYSQL Trigger

Hi, I need step by step instruction to add a MYSQL trigger in phpMYADMIN that updates one of my database tables to another table in the same database. I have a existing 4 tables that hold the form enquiry submitted data. All these 4 tables have a subscribe to the news letter. When this field is checked in the form the relevant table holding the data updates the column with "YES" . What i am looking to achieve is to set a trigger that when any of these 4 tables UPDATE and the column in that record the holds the data for the subscribe is Marked as YES then the whole new record UPDATES and ADDS to a Table that keeps all the subscribers data which is all ready in place. If this is not possible please let me know from what i have read up it seems pretty easy thing to acheive for a database expert. Please bid asap. Thankyou Sam