I imported some images for a LEGO stop motion but the animation is going too fast. When I change FPS to something smaller and export, the video is tiny. I'm not really sure what I do when I change presets, but following tutorials hasn't paid of in my case.
When you set the number of frames per second of the sequence, you are describing the rate your rendered footage will playback, whatever that footage may be. If you have 600 frames and you set the sequence to play 60 frames/sec, you'll get 10 seconds of video. If you set the sequence to play at 6 frames per second, you'll get 100 seconds of video. 60 frames per second is a speed that players like YouTube (now) accept, but 6 frames per second is not. So if you render a sequence that's supposed to play at 6 fps, you might create something that most players will not honor.
Instead, set your sequence frames per second to what you actually want to play the video at, likely 24, 25, or 30 fps (but maybe 60 fps or 120 fps if you are part of the HFR vanguard). Inside the sequence, look at all the little (violet) boxes that represent your individual images (JPG, PNG, TGA, whatever they are). Select them all, right click, and choose the menu item "Speed/Duration...". That opens up a dialog box. Change the 00:00:05:00 default to 00:00:00:02 (or however many frames you expect each image to last). In the world of stop-motion, it is common to make a movie that plays at 24 fps but in which each image is repeated (so 12 images per 24 frames). If you didn't do "twelves", then use 00:00:00:01. Select the box "Ripple Edit, Shifting Trailing Clips" and choose OK. This will create a tiny, but correct, sequence of images that can then be rendered to play back at a sane speed that all video players (including YouTube) will honor.