Alright, ignoring the obvious fail of the two other posters here, here's what you
should do.
First, are they colored? I assume so. If not, you want to do that.
Second, how big are they? If they're the size of SRB2's sprites, that's good. if not, and they're double the size, that's fine as well. Just make sure to put HIRES = 1 in the S_SKIN when you actually make the WAD. If neither of these applies, resize them so that they are either equal to or double the size of SRB2's character sprites.
Third, since these are hand-drawn, they are
not likely to work in SRB2's palette. For more on that,
http://srb2wiki.sepwich.com/wiki/Palette I recommend manually editing the images to work in that for best results. You CAN import them into a wad as-are, and the editor will convert them as it best can, but it's best to this kind of thing manually.
Finally,
http://srb2wiki.sepwich.com/wiki/Character_WAD < Use that when the rest of the conditions have been met. It will explain exactly what to do to get the character working in SRB2.