Since I posted my question, I found that if I hold down the Alt key and press the left mouse button, it brings up a box called Paragraph Text Size which allows me to enter my dimensions for the text box.
Creating a Paragraph Text is a standard feature in Elements. It works just fine in PSE 2018. When you create a paragraph text, a dialog box will pop up to allow you to enter the desired dimensions for the text box. This technique is described in the tutorial below (Step 4, Method 2).