XD I did it in a very dumb way, not that I know a better way.
(At some point in time change the background canvas to fit [or be larger/smaller for whatever you’re mixing it with] your gif)
What I did was:
1) Open gif in photoshop (To open the animation timeline go to Window >Animation)
2) CTRL+A (or Command+A for macs) the first frame
3) CRTL+C (Command+C)
Switch over to Flash
4) CTRL+V (Command+V) Paste frame into first keyframe
5) Hit F7 to create a new blank keyframe
Go back to photoshop
6) Go to the next frame
7) Select all (CRTL+A/COMMAND+A)
8) Copy (CTRL+C/COMMAND+C)
9) Paste (CTRL+V/COMMAND+V)
Repeat Steps 6-10 until there are no more frames to copy in Photoshop
You no longer need Photoshop, so exit out of it if you want.
11) Use the black arrow tool and straighten the frames so they all sit the same way. (It may help to turn off “snap to grid”)
12) Create a new layer above your pasted frames
13) Trace your heart out (not literally).
14) Fix the timing of your new flash.
The timing of the frames is probably off, you can change this by speeding the frame rate (like from 12 frames per second to 24) or slowing the frame rate (like from 24 to 12 frame per second)
Another thing you can do is add frames between key-frames to change how long one image stays, before changing to the next frame.
THEN YOU ARE
I like doing this because it really taught me about timing and how not everything has to move at the same time.
Edit: *Rewrote everything and has it saved on notepad*