New glyph

how do you apply a new glyph to a character? I can create a new glyph, but I don’t know how to apply it to let’s say the “!” or “1” character. if there’s no set glyph for these characters yet, how do i create them?

You have to set the name of the glyph. Either put the glyph name (for “1” the glyph name is “one”) or the character itself, then Glyphs will put in the glyph name automatically.