I haven't used piskel myself yet, but I have been able to gather some information from the files from the assembling machine 1.
First, the code part:
you can find the file here in this path:
data\base\prototypes\entity\demo-entities.lua
If you use N++, then you can use ctrl+f to search to the assembling machine.
In case you can't find it, here is the important part:
This part shows the size of the graphic is 99x102. This should be the size of your graphic.
frame_count is the number of frames the animation consist of, in your case 33 frames, judging from the number of pictures you use.
I have no idea what the line_length or shift does, I would recommend that you experiment with it, or use the number from the assembling machine, as it looks like you use the same frame size.
Regarding the sprite sheet part, I would recommend mimicing the assembling machine, perfect grid with one pixel in between. I have no idea how to make piskel do it for you, but you can do it with a normal image program with transparency.
Paint wont work as it makes transparent backgrounds black because it doesn't support the alpha channel. If you try then you get a black box around your sprites.
I hope this helped you out
