Use arrow keys to move about the map.

Go to a yellow castle to interact with a kingdom. You can decide to attack or negotiate with it (using A and N respectively) by entering in the input text box that appears. If you attack it and fail, you will lose strength. If you win, you will gain strength. If you negotiate, you will gain a little strength but not all kingdoms can be negotiated with.

You can gain bonus strength by performing a task in a short amount of time (set at 15 seconds, at the moment). Not all kingdoms have this bonus as I ran out of the allowed number of events. (If I wanted to purchase Construct 3 I could have more events and finish this)