First, you need to connect both games' DOSBox applications. To do this, please follow this article.
Once both games are connected to each other, both players need to go to the in-game Options menu, then click Network -> IPX. Once this is done, you should see a list of connected players almost immediately.
The rest is straightforward - go back to the main menu, then one of the players creates a game (make sure to set up a correct number of compiuter and human players), the other joins, and once everyone is connected, the multiplayer game will start.