Interfacing ReRAM in-memory computing within a system

Can't speak for ReRam specifically, but for other hardware systems that carry out the computations on the hardware level, the electronic interfaces are usually a large vector of analog signals and the outputs are also large vectors of analog signals.

If your target system is a digital computer software, then you will have to make sure, that this software writes values to the DACs and reads backs values from the ADCs.

Of course it is possible that the neuronal hardware is trained such, that it will accept a vector of simple HI/LO digital logic level signals instead and will output at a digital logic level. In that case the software task will be writing and reading these digital bits instead.

If ReRAM-based IMC has to be used in practice applications, how would software applications interact with the ReRAM-based IMC accelerator?

ReRAM can be used as a memristor or setup as a phase change material used in a binary configuration. There are some research applications seeking to replace NOR ram with ReRAM cells in a similar configuration. In these applications you would read a low or a high voltage with a comparator.

If used as a memristor, you would need some kind of ADC at the end of the cell (or chain of cells) to measure the exact voltage. In these types of applications, you would probably use the cell to store the memory of the neural network, which can have a range of values.

Neural networks are trained on data to give a certain output based on certain inputs. The values of the neural network don't mean anything, it is a black box (although there is currently research on trying to understand how neural networks store information). So the software would be the same as training any other neural network.