Open the dialing screen and then press #, *, Menu, Right key. Don't pause between key presses, or you will have to start over. On units with SIM cards, scroll down until you see "IMEI/SIM ID" and press Enter. From here you can view your IMEI, SIM, and on some units, your MSN. The first fourteen digits are displayed; the fifteenth is always a 0.  On older units without SIM cards, continue to hit the Right key until you see IMEI [0] on the display. The first seven digits are displayed. Write these down, as only 7 digits are displayed at a time. Press the Menu key and then the Next button to display the next seven digits.  The fifteenth and final digit is most often a 0.

How would you rephrase that briefly using Vietnamese?
Bật nguồn điện thoại. Xác định số IMEI.