You choose a particle effect that has a transparent background, put the particle effect on a Video track below the video track.
If you choose a particle effect that does not have a transparent background, you can modify the particle by removing the background.
Carl312: Windows 10 64-bit 8 GB RAM,AMD Phenom II X4 965 3.4 GHz,ATI Radeon HD 5770 1GB,240GB SSD,two 1TB HDs.