Worried, how to start a Tkinter based Python GUI on Raspberry PI Startup

Follow the steps below

1. Open Terminal in Raspberry PI.
   
2. Write the following commands:
   

sudo nano /etc/xdg/lxsession/LXDE-pi/autostart

You will see a text file.

3. At the end add a line:
   

@lxterminal -e python3 /home/pi/<your_directory>/<your_file>.py

4. Press "ctrl+x" and then press "y" and press "Enter Key" twice.
   
5. Type "sudo reboot" to reboot your pi.
   Note: Use your own directory and program replacing <your_directory> and <your_file> respectively.