Global Sharing Option
By default when you installed theme. Sharing button displays next to main menu only on single page for example. single post, single gallery etc. You can also enable sharing button on all pages. Simply go to Appearance > Customize > General > Sharing and enable “Enable Sharing Button To All Pages” option.
Single Post Sharing Option
On single post page. Normally it displays post title and its content. Reader can share post content using global sharing button which displays next to main menu. However if you want to make sharing option more visible. You can enable this option in Appearance > Customize >Blog > Single Post > Display Sharing Buttons on Single Post Page Content so theme displays sharing buttons after post content.