To open the SIM tray using a SIM ejector pin or tool, you can follow these steps:

1. Locate the SIM tray: The SIM tray is usually located on the side of your phone. On most OnePlus devices, including the OnePlus 8, the SIM tray is located on the left side of the device.
2. Find the SIM ejector pin or tool: OnePlus devices usually come with a SIM ejector tool included in the box. If you don’t have the original tool, you can also use a small paperclip or a similar thin, pointy object.
3. Insert the SIM ejector pin: Take the SIM ejector pin or tool and insert the pointed end into the small hole located near the SIM tray. Apply gentle pressure until you feel resistance.
4. Eject the SIM tray: Once you feel resistance, push the pin or tool firmly but gently into the hole. This should trigger the release mechanism, and the SIM tray will pop out slightly.
5. Remove the SIM tray: Use your fingers to pull out the SIM tray completely from the device.

Now you can insert or replace your SIM card(s) into the appropriate slots on the SIM tray. Make sure you align the SIM card correctly before inserting it back into the phone.

6. Reinsert the SIM tray: Once you’ve inserted the SIM card(s), carefully push the SIM tray back into the device until it sits flush with the phone’s body.

That’s it! You have successfully opened the SIM tray using a SIM ejector pin or tool on your One Plus 8.