Carlton Banks pretty much explained everything, however if you are going to use your fresh Ubuntu install for more than just your online armory, i would install the package via
apt-get instead of
dpkg.
So, instead of:
8. if the hashes (long string of letters and numbers) match, dpkg -i armory.deb
you can do (when inside of the directory):
apt-get install ./armory.deb
It usually is recommended to stick with apt-get, because it doesn't just install a package, but also looks for dependencies since it is a package management software.
This makes it easier for you to remove or change packages later compared to simply just
installing it using
dpkg.
apt-get uses
dpkg to install the package in back end, but has additional features (scanning for dependencies, notifying when they can be removed, etc.).