To delete a graph from your Saved Graphs, first make sure you are logged in to your Desmos account.
To view your Saved Graphs, click the three horizontal lines in the upper left hand corner.
Click on the "x" next to the graph you're looking to delete. A message saying "Deleting this graph..." will show up as well as a Cancel option. You have 5 seconds to undo your deletion by clicking the Cancel option.