Thanks ^^
It depends on the program you use. In Flash you chose the size (in px) when you save the file as a .gif, it repeats itself automatically. That's the cool thing about vectors, you can chose whatever size you want without dataloss/blur etc.
In GIMP the animation will be the same size as your canvas/picture, so when it's too big just shrink it down before saving. The program guides you through the rest once you export the file as .gif - the framrate, if you want autorepeat, if you want the frames to overlap or replace each other... it's pretty self-explanatory, just follow the steps and read what the program tells you ^^
I never used other programs for saving my animations so I got no experience there
I'm sure Google knows help