Extract the content of the .rar file anywhere on disk.
Drag the timelineMarker.mel file in Maya to permanently install the script.
The UI elements are added to the timeline menu and can be accessed by right clicking on the timeline. You have the option to change the color of your marker points and also add comments where necessary. ToolTips will appear to show the comment while hovering over the timeline. The markers are stored in the maya file.
The hotkey function can be used to setup hotkeys to manage the timeline markers. There are three options, this is to either add, remove or clear the markers. Make sure the language is set to python.