Need help with recording casio cpd s-350 and singing directly to computer

[Dnnyboy]

Hello everyone so I am thinking of making mp4 files of myself playing and singing on my piano.I looked into how I could do that directly to my pc to make it sound nicer and I have come to you all for guidance so heres the equipment I have gathered so far.So I have a 4 pole 3.5 mm audio cable male on each end and then a 4 pole 3.5 mm audio splitter (so one side is male the other side is two female one for microphone and one for headphones)now I believe if I just connect the 4 pole 3.5 mm audio male cable from the casio to my pc thats gonna record like a mono sound I believe which doesnt sound very good so I think you have to connect the audio splitter to the casio first then connect the 3.5 mm male cable to the microphone port from the audio splitter to the microphone port to my pc and thats gonna make a better sound I believe but Il have to test that when they arrive.My question is if I then also connect a usb microphone would my pc pick up the piano playing and my singing at the same time while recording from those two sources?

Thank you for your help since Im not very knowledgeable in this field since I started last week.