I have an explosion gif over the main video and a blood splatter image. I want the splatter to be behind the explosion, but right now it's over it. How can I change the order of these objects?
In timeline mode, the video is made up of tracks seem from bottom to top eg track 3 is in front of track 2 which is in front of track 1. To see through parts of a layer you will need to go to 'Video effects' and chose an appropriate 'Chroma key' (this is in VPX2 but may be called something else in your program / version). If your explosion is against a black background pick 'Black box' effect and the black part will become transparent to show what's behind.
There are many tutorials made by users including some on chroms effects.