Assuming it’s still using a raspberry pi 4, this should all apply.
Download an image of the raspberry pi operating system.
Take that raspberry pi image and flash the micro sd with something like BalenaEtcher or Raspberry pi imager.
Once you have the image installed on the micro sd card and boot up the raspberry pi, you’ll need a keyboard and preferrably a mouse for setup.
Preferrably, use a more optimized browser like mercury to launch these webpages (make sure to download the ARM64.deb version since raspberry pi 4 uses an ARM cpu and its os is based on debian).
sudo dpkg -i ./[FILE NAME].deb
If you opt to use another browser, please note that you will have to modify the script files in order for it to work properly. In addition, some browsers may not have the same functionality as firefox or mercury.
With that up and running, you will now have to setup your browser.