Hi,

There are mainly two ways to start a program at startup : with or without graphical session (desktop).

With graphical session, I guess you have to setup Raspbian to start on desktop automatically (raspi-config).

1. With graphical session : ~/.config/lxsession/LXDE/autostart : https://www.wikihow.com/Execute-a-Script-at-Startup-on-the-Raspberry-Pi
2. With graphical session : ~/.config/autostart/startpd.desktop : https://wiki.lxde.org/en/Autostart
3. Without : /etc/rc.local : https://www.raspberrypi.org/documentation/linux/usage/rc-local.md
   

I hope it helps,

++

-- 
Jérôme Abel
http://jeromeabel.net