[Silver Knight]

Alright, I'll try to answer your question.
1. You can try to find a program to do what Giffy does, but for PNGs.
2. I use Giffy to set transparencies of GIFs, then I open them in Photoshop and save them as a PNG (preserves the transparency too.) So if you have Photoshop you can try that.
3. Use the add sprite definition button. Where it says SPRITE, type in the file name or select an attribute/other thing from the drop down menu.
You can type a description in the description box, like "Sword Up Right".
Be sure to set your Sprite index, or you will overwrite pre-existing sprites.
In the right area you get the boundaries and dimensions of the sprite
to be added from within the image file. (It helps to have your image
in Paint, or a similar program, so you can find the widths, lengths, X and Y
positions of what you want to add with ease.)

That's about it for adding sprites. There is also a button to get images from
other Gani files and add them in, that comes in handy if you
are making a bunch of ganis using the same sprites (so you don't have
to input them by hand each time.)

Then you just drag and drop onto the frame, make new frames,
copy frames, etc.