After entering the web interface, a terminal will open. All workspaces are sourced automatically, so you can run any command directly in this terminal.
If the terminal window is not visible, right-click to open a menu. From this menu, you can select the terminal, as well as launch ROS GUI tools and ChassisTuner.
If a command is too long, press the blue button on the middle-left to expand the Clipboard section. You can then paste the command into the text box and right-click in the terminal to paste it.
