how to add a background to a screenpack

[tiggercmw20]

I just want to know how to add your own background to a screenpack I can't figure it out if any knows how can you help me out thanks

[Draco]

first resize the image to 320*240, 640*480 if you want to change the select screen background from Hi-Res mugen.
then just convert it to 256 colors and save it as a pcx file (you can do this very easy with irfanview) then you can use mcm or fighter factory to open the sprites and add them to the .sff file.