You can simply search for Calendar in Weebly app market and add it to your site. After adding the app to your Editor page, click on it to.
Click on the Add Event button to add new events.
Click on the Manage events to manage the existing events.
To add a new event fill out your event title, set the dates and select an event color. Switch off the “All Day Event” if you want to set event Start and End hours.
Scroll down the window to add an event image, description and files (“Details” section). Using the “link” function you can add hyperlinks to your event description.
You can, as well, add the advanced details of your event (venue, organizer) and link it to Google Maps.
When all the details are added, just click on the Next button on the top right corner to save your event as a draft or publish it.