using the script/command gifmerge

gifmerge is used to combine multiple single-image GIF files into one Animated-GIF file.

gifmerge -help

=== GIFMerge Rev 1.33 (C) 1991,1992 by Mark Podlipec
    Improvements by Rene K. Mueller 1996

Usage:
gifmerge [-<r>,<g>,<b>] [-<delay>] [-l<loops>] [-d<disp>] *.gif > anim.gif

   -<r>,<g>,<b>   set transparency, ie -192,192,192, default: no transparency
   -notransp      set transparency off (after you used -r,g,b before)
   -<delay>       set delay of between images in 1/100th secs, ie -100
                  default 50 (0.5secs)
   -l<loops>      set loop counter, ie -l0 (ever) or -l1000, default no loops
   -d<disposal>   set disposal 0 = no action, 1 = no dispose,
                               2 = restore background (default)
                               3 = restore previous
   -pos<x>,<y>    set offset position for image
   -nopos         reset offset position (default)

   or look at http://the-labs.com/GIFMerge/