To do it you need an array of addressable switches, with a set for the horizontal rows and a set for the vertical columns.

We have used Allegro serial to parallel chiips ULN 5832 I think for the column drivers, I can't remember what we use for the row drivers.
The column drivers sink current. The row drivers source it. The LED's straddle the intersections.

Anyway data is sent out via three port pins on the uC to strobe the LEDS, by judicious control the illusion of scrolling is achieved, if the refresh rate is kept above about 60Hz.

Hope this helps

Steve