In Gmail, you can add events and manage the calendar with the steps below:
Step 1: Login your Gmail account (please refer here to open one if you do not have an account yet);
Step 2: On the right panel of your Gmail account, click the "Calendar" icon;
Step 3: Click the "Create an event" icon;
Step 4: Enter the title name, set up the time and type the description;
Step 5: Click the "Save" button at the bottom, and the event will appear in your calendar;
Step 6: You can open the calendar from Gmail by clicking the "Open in new tab" icon.