Here's a clue: The difference between displaying text on a LED matrix and scrolling text on a LED matrix is the text.
Show this scrolling by...
how this scrolling by...S
ow this scrolling by...Sh
w this scrolling by...Show
this scrolling by...Show
this scrolling by...Show t
Figure out what text you want to display.
Display that text. Wait some period of time.
Alter the text.
Display that text. Wait some period of time.
Alter the text.
Display that text. Wait some period of time.
Alter the text.
Display that text. Wait some period of time.
Alter the text.
<repeat as often as desired/required>