multiple files open in their own excel 2013 window

New Contributor

I was recently switched to excel 2013 and I am having trouble adjusting. I typically have at least three excel spreadsheets open at once. they used to be within the same window and I had them sized down so I could see a portion of all three at once. now they all open in their own window so there are separate toolbars/ribbons for each. is there any way to put them back into one window?