You may get discouraged when you see how complex it is, to that end here are a couple of tutorials that apply to the current version of Fritzing (many of the others are for older versions):
I lately learned there aren’t links to the videos in Old_Grey’s tutorial so you need to do a google search for the title and then they come up on YouTube. I’ll do the first one in a bit (I am currently making a part for someone else) and you can, if you like, use it as a base to try making the rest of them. We could use more people familiar with making parts, but finding them is being hard. You need to be familiar with a SVG editor (I use Inkscape which is open source and thus free, but Illustrator or CorelDraw will also work, Illustrator is a little difficult because it makes assumptions that don’t seem to be changeable about how the svg is laid out (some of which Fritzing objects to!) There are forum posts on what has worked for folks (Inskcape on the Mac is suboptimal due to being a X app for instance so you need to import the svg to parts editor the export it as Fritzing will change the svg to what it wants!) We are always happy to help people make good parts 
. There used to be a handful of folks that could do it but is currently mostly down to me.
Peter