This is the tab, where you start working with a phone. You select phone model and desired connection speed (in almost all cases this item can be left in AUTO state), connect phone to box either via USB Service socket (for phones with USB interface) or via RJ-45 socket (for phones with serial interface) and press Connect button.
After some time MSS will recognize your phone and display various information:
Model selection box lists all the phone models currently supported by ODM Service Software and allows you to select one you want to connect. Connection speed box can be used when you have problems connecting particular phone (you can try to lower the speed in this case).
Repair mode checkbox is used when Acer phone has damaged bootloader and cannot be connected in a usual way. In this case you cut the track (detailed instructions are available in the sticky post on ODM support forum) and connect phone with this box checked.