Open Autorouter, then select the entire two NETS, right mouse button, select make a differential pairs.
After reselect nets, then differential pairs, then properties, now you can edit differential pairs properties.
Remember Check if the general rules are not in conflict with the diff pairs properties !
In pads router
1.Go to project explorer and set the two nets as a differential pairs.
2.Set the constraints such as trace wdith and clearance
3.Now select the route command and route the differential pairs if u select one net automatically other will be selected.
Why use differential signals? The industry's need for speed means higher bandwidth for data transfer rates. The data transfer scheme implemented as differential is faster, requires less power and is more resilient / immune to noise if implemented correctly. Differential signaling also reduces EMI, since the opposite currents carried on the two traces lead to cancellation of the electric and magnetic fields at long distances. Similarly, differential signals are less sensitive to crosstalk.