You can make a meeting or task on the Outlook webclient by just dragging and dropping the email provided you are in the My Day view. My Day is on the top left of your screen and looks like a calendar with a check mark on it. Select that. Drag your email to the appropriate spot and complete the dialog that appears.
Be careful about creating an “Event”. This makes a meeting and not an appointment so you might need to remove the other email recipients and add yourself as the only meeting attendee to avoid sending this to everyone on the original email. Of course you can leave them if you want to meet with everyone on the email.
This video shows some of the steps.