Arguments specify which adjustments need to be used when you run the project. They can be found inside of the webui-user.sh file, typically as the following:
# Commandline arguments for webui.py...
# export COMMANDLINE_ARGS=""
On a fresh install, the quotes are empty. If you find some command-line arguments that you want to try out, just uncomment the export line by removing the #, and adding the arguments between the quotes with spaces separating:
export COMMANDLINE_ARGS="--xformers --medvram --no-half --upcast-sampling"
Going forward, every time you run ./webui.sh, It'll use these arguments.