It's always difficult to explain something without a diagram and sometimes it's difficult even with one, the radio interferometer telescope is a case in point so I thought I'd make a GeoGebra simulation to show how it works. Here are two stars passing overhead . The radio waves from each is detected by two detectors on the Earth. Each detector detects the waves from each star. The signal from each detector is added together to give the traces shown. The resolution is increased by increasing the separation of the detectors. Try varying the separation in the simulation below.

The way I did this in the simulation is to take the path difference from a star to each detector, turn this into a phase angle then use this to find the amplitude of the combined signals (by rotating two vectors).

Notice that when the detectors are close together the two peaks overlap so would be difficult to resolve. Hmm, not easy to explain with a simulation either.

(ctrl + F clears the trace)