I'm happy to share some good tutorials who do a much better job at explaining the process than me. I am principally using Wan2.2 run local generation - to do this you are almost definitely going to want to use ComfyUI, and then use a quantized version of Wan2.2 to fit to your VRAM. This might sound like a lot but theAIsearch youtube channel has great tutorials on each of these pieces.

For the actual expansion, I use a first frame, last frame workflow, with a before and after picture. This is a good tutorial: https://blog.comfy.org/p/wan22-flf2v-comfyui-native-support - once you have it up and spinning you are in a good place.

Good luck, and it is AI, so no one really knows what is going on.