How to keep 2 excel sheets open side by side?

For the project I have been working nowadays, I need to work with Excel frequently.
I need to compare two excel sheets so I need to keep them open side by side. since they are both excel documents, MS tried to save the memory for that and does not allow me to do so, unless you follow these simple steps:

1) Click on the office icon and select excel options.
2)Go to the Advanced tab and scroll down to general section to click ignoring other applications.

That is all!!!