Locate the package folder "eyeRigTool" inside maya environment variable
Windows C:\Users<Username>\Documents\maya<version_number>\scripts
Linux $HOME/maya/<version_number>/scripts
macOS $HOME/Library/Preferences/Autodesk/maya/<version_number>/scripts
Write the following code in the maya script editor
from eyeRigTool import ui
window = ui.UI()
window.debug_UI(300,200)