Demo version only works on demo accounts.

To install the tool, open "Data Folder" from MetaTrader "File" menu, then open the "MQL5" folder and put the file in the "Experts" folder. 
It will add to MetaTrader Expert advisors (restart MetaTrader if needed).

To run the Order Manager for the first time, in the Metatrader option dialog (Ctrl+O) tick the "Allow automated trading" option in the "Expert Advisors" tab, 
then attach the Order Manager to the chart, and in the "common" tab of expert properties dialog tick "Allow live trading" option.

If you have any questions ask me in the comments or via private message.
https://www.mql5.com/en/users/amir_atif