You can add your email address in FUSE social floating sidebar by going top Fuse Social > Social Icons, you just need to add mailto in start of the email address.
As shown in the following screenshot:
So as shown in the example, you can add the email address as mailto:firstname.lastname@example.org.
Mailto link is a type of HTML link that activates the default mail client on the computer for sending an e-mail. The web browser requires a default e-mail client software installed on his computer in order to activate the e-mail client.