MFC Multi-Client is an old application that is not compatible with all DVR devices. You should find a user guide in the Help menu, but my recommendation is to contact the device provider and ask them for a program compatible with your DVR model. Also, they will provide you a manual that will enable you to connect the device to your software. In general, you need to launch the program and to click the Add Device button. After that insert the IP address of the DVR device in the provided field and click OK. You should find the IP address of the DVR in its booklet.