It helps if we know what version of the program you're using.
But, assuming you're on version 15, go to the Text menu and start a new title. In the Title Adjustments panel, go to the Shapes tab and select and draw a rectangle.
Here's the trick from my book and our friends at Muvipix.com. With the rectangle selected, go to the Style tab and apply a text style to the rectangle that includes an outline (or stroke). Then go back to the Shapes tab and click the Color button to open the Color Properties panel.
On the Color Properties panel, set your fill color to no color (the slash above and right of the color picker) and the stroke to whatever color you want your outline to be.