This screen allows you to do sophisticated operations such as creating exact circles, measuring distances along lines, changing marker styles in bulk and more!
Convex Hull option will create a convex hull (polygon) from a group which joins the points together.
To open the Operations & Analysis Tool panel (A&O), either click the gear icon on the top right corner of the workspace above the open Layers panel OR click MENU then the double gear icon with O&A noted.
If the overlay panel is not visible, click the perforated design on the far right side of your screen where you see 'Layers'
Choose the Analysis - Analysis - Hull - Convex Option from the A&O panel: