Hi,
1) put antennas so that the beams are forming some angle. If you have a distant source of signal in space, it will produce different amplitudes at antenna outputs and you can conclude about the angle of arrival by comparing two output signals
2) you can have both antennas set to have beams in parallel and connect both outputs to inputs of a rat-race hybrid (sum/difference circuit). This is called monopulse detection system. Again, comparing the output signals from the coupler the angle of arrival could be found