Assuming that it is a single pole relay.... it should have two wires for the relay coil and two wires for the load. On the relay cap, it should
have a diagram or terminal numbers.....are there?

The smaller pair of wires is the relay coil circuit while the two larger terminals and wires are the load (starter)....perhaps this helps.

You should be able to put 12 volts across the relay coil terminals and hear an audible click....you cannot hurt the relay if it is connected backwards during your test....you can short out stuff if it is connected to other parts of the car circuit so disconnect all wires going to it during testing.

If no other info exists, there are 4 terminals and 4 wires.......is that
16 combinations to test? Really, you only need to test 4 terminals and two wires to find the coil circuit....fewer guesses.