Please help, really cannot figure out how to add transparent sequence over video footage

[Birds2112]

I do 2D animations by hand. I draw every frame on paper with marker and scan them into a folder on my computer. I know how to turn that into an image sequence in after effects, but I want to take video footage and have it playing underneath the image sequence as a background. I need to make the image sequence completely transparent and resize it down so it's smaller than the video underneath it. Why is this so impossible to figure out? I just want a video playing underneath my animation.

Please do not suggest a different way of animating!! I work by hand, I'm not willing or able to just change mediums and start animating on an iPad or something, I just need to figure out how to get an image sequence transparent and layered over a video. Best example I can think of would be those scenes in SpongeBob where the characters are animated over video footage outside of the ocean

[Mylenium]

You may work by hand, but you still have to create the transparency somehow and that means masking it out with digital tools. Depending on your art style and whether the images are colored or not and in what type of coloring you use, this can be as simple as taking e.g. a black & white line drawing and applying it as a matte on itself or extracting transparency from inverted luminance with channel operations just as it can be infinitely complicated if you use fine hatching patterns or aquarell colors in pastel tones. Point in case: The "figuring out part" can be quite complex and of course you won't find anything specific just by typing "make stuff transparent" into Google. To get to the point: Show us examples of your drawings/ artwork and we can tell you how to best proceed.

Mylenium

[Birds2112]

Thank you--I definitely know and accept that I'll have to use digital tools to pull everything together, I just meant that every time I try to solve this issue instead of suggestions for what I'm asking everyone tells me to start drawing on a tablet instead and I am terrible at that!

I don't have my computer nearby right now but this video I'm linking is exactly what I'm trying to do! She has a still image as her background, and I'm trying to make my background a video but I would also like to learn how to use a still image as the background. 

https://youtu.be/Ui8q4GwApcw 

Let me know if this isn't a good enough example and I'll try to update with my own stuff later but she is basically doing what I do, frame by frame and then scanning and creating an image sequence. I use a dark marker instead of pencil so I imagine that would make it simpler?