There is no guarantee that buying 2 single sticks of identical ram will work in dual channel configuration, but there is a good chance as it's Corsair ram(I have had issues in the past with buying single sticks for dual channel). For dual channel configuration to work they must be in the correct memory slots. Generally speaking manufacturers choose a different colour for pairs in dual channel ie. 2 blue slots and 2 black slots. If yours are like this make sure the ram is in same colours, but it may not be like that as I have seen variations where all slots are the same colour.
What motherboard do you have? Best advice I can give with the info given is to determine your exact motherboard make/model and download the manual from the manufacturers website, it will be clearly laid out in there how to configure the ram in dual channel mode. Also just for reference, cpu-z doesn't indicate dual channel for me either but i'm running dual channel so don't be too concerned. Have a look when your system boots post(black with white writing) as it may say 'dual channel mode' or similar, if not go into the bios and have a look for something confirming memory mode.