Bellow installation procedure uses only command line approach, because this is the simpler way to follow instructions just by copy-pasting the commands in terminal. This instructions are tested with the currently supported versions of Ubuntu.
This use a script with all the required command to setup the repository, If you prefer to do it the manual way please look at the Debian instruction.

1. Copy and paste this command to a terminal to install the Skychart repository:

   bash <(wget -qO- https://raw.githubusercontent.com/pchev/skychart/master/setup_skychart_deb.sh) 

   Be sure to select the Beta version if you install on a recent distribution.
   At this point you can install the program using the Software Center or continue using the command line with the instruction below.

2. Update repository:

   sudo apt update

3. Install Skychart without full dependencies (does not install the packages required for the Artificial Satellites display, you can install them later):

   sudo apt install --no-install-recommends skychart

4. This is all software you need to install if sky will be observed with naked eye. But if you like to see some deep-sky objects (e.g. galaxies) and stars that are not seen with naked eye then install additional packages (this will download several MB of additional software):

   sudo apt-get install skychart-data-stars skychart-data-dso skychart-data-pictures

5. Launch Skychart from terminal:

   skychart

   You will also find the Skychart button in the main menu. Please never run skychart as root or with sudo.

6. The program starts up, it takes several seconds to initialize, click Next button.
7. See the quick start guide for more information about the different use of the program.