You can manually download MEC from Webnus panel or WordPress plugins repository, then go to FTP and to the folder wp-content/plugins. Then upload the zip file there, and extract it in the same place to replac the previous files. And the update is done.
After activating MEC, you will be redirected to the “intro page”, which you can always access from M.E. Calendar in MEC menu and there you can find all the information you may need, including all the details about your end users’ reservations.