Snaps can be run with snap run, so for the example in the question
snap run ubuntu-calculator-app. But that is annoying so it is better to add snaps to your path. If the app is a gui, once you open it you can right-click on the launcher icon and select add to dash.
Snaps are not in your path by default on 16.04. They are stored in /snap/bin. Since snaps are a system-wide installation it would probably be best to add this directory to your system-wide path. This is done via the file
/etc/environment. The following can break stuff, so you should backup the file before editing it
sudo cp /etc/environment /etc/environment.bak. Use an editor with sudo to open
/etc/environment, and add
:/snap/bin to the end of the PATH entry. Make sure you restart your terminal or
If that still doesn't work, you need to make sure your user .bashrc file has added /etc/environment to its sources.
grep "source /etc/environment" ~/.bashrc will echo that line if it exists. If it doesn't
echo "source /etc/environment" >> ~/.bashrc will add it.