A little more detail:
a. Each of the things you are calling "story boxes" are known as a Passage.
b. You can 'connect' two of those passages together using a link.
c. Each story format can contain a number of different link types, but all story formats support the standard Markup Based Link. There is an advance version of the markup based link type which is know as a Setter Link but only SugarCube currently supports it.
d. The standard Markup Based Link can be used in a number of different formats depending on exactly what you want to do with it:
[[The Link Text and the target Passage Name are the same]]
[[The Link Text|And the target Passage Name are different]] (SugarCube syntax)
[[The Link Text->And the target Passage Name are different]] (Harlowe syntax)
[[The target Passage Name<-And the Link Text are different]] (Harlowe syntax)
e. All story formats support both the SugarCube syntax and the Harlowe syntax.
You can use those characters within the Link Text part of a markup link.