With the caution that you want to be vary sure you are in the correct directory (because this could erase your entire system if done incorrectly, so make sure you have a backup!):
cd ~/Downloads/fritzing-0.9.3b.linux.AMD64
(or the directory where you run Fritzing from)
(optional but wise)
ls
(to make sure you are in the Fritzing directory where you think you are)
rm -r *
(this is the dangerous part as it will erase everything below this). That will remove all the Fritzing code and a new tar will do a new install.
What kind of problems? I just untarred the distribution file and ran Fritzing.exe on 18.04 without issues. If you have installed, and started then aborted a parts update you may need to clear the user directories (assuming you have no sketches or custom parts loaded this will do the trick):
when Fritizing is run again it will create new directories (and probably do a parts update which you need to let complete before stopping Fritzing to avoid corrupting the database.)