Yes it matters. These should work if they're .ttf files.
CrimsonText-Regular.ttf (or just plain CrimsonText.ttf)
CrimsonText-Bold.ttf
CrimsonText-Italic.ttf
CrimsonText-BoldItalic.ttf
If you have problems after you've loaded them you need to double-check the
CrimsonText part of the name. It needs to match the internal font name. So if internally it's called
Crimson Text Medium then use this as the first part of the 4 filenames instead.