Hi there,
I should start that I have no idea how to do it by myself and I am under great impression of you people doing these gorgeous fonts out here.
I need 7 letters of font to be edited just slightly, have jpg file of those letters done but don't have idea what to do with it now and how to collect it with remaining letters to new font.
If anybody would be so kind and willing to help I will greatly appreciate it.
I imagine that is 5 minute task and I have wasted half day on in and still don't have a clue how to do it.

1) JPEG images are useless, because they use too many colours. Your source images need to be in black and white, or in colours that will turn black and white, if saved as a monochrome image.

2) No one is going to show you how to make changes someone else' font. The person who made the font wanted it to be the way it is.

3) It takes considerably more than five minutes to edit a font glyph.

I add that JPG is a bad format for the drawed images because the compression used by JPG is destructive. It means that it make changes in the image and damage it.

For an image like a picture, it's almost invisible (if the compression factor is not to high) but for a draw, il can be desastrous.

If you want to keep the quality of a drawed image, use tha PNG (or TIF if you don't have transparency) format.

And, like said metaphasebrothel, the JPG manage only the 16 millons colors images. PNG and TIF adapt the level of color (2, 16, 256, etc.) and the size of the file change in the relative with this level of color. So, for a 256 colors, the size of a PNG or TIF file is many time besser than a JPG file (and without loose quality). And for a 2 colors, the PNG and TIF is ever lighter than a JPG.

Forget the JPG for work. Use it only at the final to transmit a file (but keep tha PNG source).