I’m trying to pair a Dell KM7120W Wireless Keyboard and Mouse to second pc with a Dell dongle in each pc

One Dell Laptop and One Pro Tower Have aDell Dongle in each pc

I can pair both keyboard and mouse to either pc on channel 1

How do connect to the other pc with dongle on a different channel?

I thought you needed a dongle on both pcs. Or is it that you can only pair on one pc with a dongle (channel 1) and you cannot connect via the other dongle to channel 2? Bluetooth only? 
like my Logitech Master Mice?☹️🤔