Page titles show in the hero at the top of each page, the page tab, and in the 'explore' sections.
Find the page you want to edit.
Hit the profile icon in the navigation bar, expand 'control panel' and select 'edit page' from the expanded menu.
Across the top are a number of options, select 'Properties'.
In the 'type and title' section at the top, change your title.
Scroll to the bottom and hit save.