Both answers are correct, but the way they're being presented will create a quick black or transparent (drawing a blank on the name, I'm referring to the white and gray squares.) background for a moment in between the render and animation. So, you'll want to include the first and last images of the animation. Especially so for loops.
Something like:
Python:
image ch1s13first = Movie(play="images/s01e01/ani/ch1s13first.webm", loop=True, start_image="images/s01e01/ani/filename_060.webp", image="images/s01e01/ani/filename_119.webp", framedrop=False)
Insert the proper paths for your files, change the names as needed, and you'll have a working animation without having to fuck with Cutscene. If it's not a loop, then just change it to "loop=False".
Then in your script file (or wherever your dialogue and such is), just add it as you normally would for a new render/image.
Python:
scene xxx1 with dissolve
mc "Hi, my name is Connor, let's fuck."
m "Connor. . .I'm your mom."
mc "Not if we use our imagination!"
window hide
scene ch1s13first with dissolve
Size is nearly entirely unnecessary unless you're making a 4K version of your VN or something of the nature. You should be downscaling everything (except for the main menu, perhaps.) to 1080 before releasing anything.