The Woocommerce Event Manager plugin has a wonderful template override feature. So You can Modify or add any content to any template. If you want to change/add a new social share icon in the Share button template, Please follow the process below.
First, go to your theme folder and create a new folder name mage_events, Then enter into this newly created folder. Create another folder into it name it as single
Now go to the plugins/mage-eventpress/templates folder. Copy the share_btn.php file. Go back to your theme folder then go to mage_events/single folder and paste the template file.
Now you can edit this file as your wish, You can add a new share button or change the existing button.