How to start a snap package
Solution 1:
Just log out and log back in. If you are upgrading from an earlier version of 16.04 development release you will not have /snap/bin in your PATH environment variable.
Solution 2:
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 source /etc/environment
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.
Solution 3:
Just including the path to the /snap/bin in the local ~/.bashrc works for me.
Run the following
echo "export PATH=$PATH:/snap/bin" >> ~/.bashrcsource ~/.bashrc