As per the Prerequisites page from earlier -

The Bet Machine uses 3rd Party Software called Gruss Betting Assistant to place bets on the Betfair Exchange. The Bet Machine connects to Gruss through what is called the COM interface. The COM interface allows The Bet Machine to directly communicate with Gruss Betting Assistant. Gruss Betting Assistant places all bets. The Bet Machine simply tells Gruss Betting Assistant which selection, what odds and what stake to use.

Before we can connect The Bet Machine to Gruss Betting Assistant we need to turn this feature on in Gruss.

All the screen shots on this page are taken from Gruss Betting Assistant.

In Gruss Betting Assistant --> Go to Options --> Preferences

Then go to the COM Server Tab. Make sure the COM Server is enabled. Then press OK.

That is all there is to it. Gruss Betting Assistant is now setup to accept connections and instructions from The Bet Machine.