Easiest is to right click on the part in the mine parts bin and select export part. That will write the part (the .fzp file and the 4 svg files) to a .fzpz file. Your likely problem was pins defined in the .fzp file that didn’t exist in the breadboard svg file which will cause problems.
While it is easiest to start from an existing part (required in parts editor because it can’t create the complete set of files) it is possible to make a part from scratch if you know the file formats well enough. These two sets of tutorials on making parts apply to the current versions of Fritzing (most of the rest are for previous versions, pre parts editor.) The videos cover parts editor I think, I don’t use it that often so mostly ignored it.