The button at the top starts a lecture and puts it above the others, because the newest one is the one being written. Give it a heading, which is yours to name: a date, a topic, the lecture number, whatever you find it by later.
Every lecture is closed when the page loads. The list reads as headings, and you open the one you want.
Typing saves on its own. Cmd or Ctrl + B for bold, + I for italic, + H for the last colour you used, and again to take it off. Selecting text brings up a small bar with bold, italic, a bullet list and the four colours. Typing - or 1. starts a list, ### starts a heading, > starts a quote, --- draws a rule, and Tab inside a list indents.
The three dots at the end of a heading open a small menu, and the one thing in it today removes that lecture. Choosing it asks first, and Keep puts the row back untouched.
Everything written here stays in this browser. These notes live on the device you are using, beside the tick boxes on the GNG2101 hub. They survive a reload and a closed tab, they are sent nowhere, and clearing your browsing data removes them. Copy anything you cannot afford to lose.