Text in 2nd and 3rd text frames needs to equal that of the 1st after entry...

[defaultwmnv51s0wmkl]

I have 3 text frames that need to be filled with the precise line of text, although perhaps with different type size and font. How can I make it so that after I enter the text only once into textbox #1, it will automatically fill the 2nd and 3rd text boxes with the same text after hitting some refresh key?

Many thanks.

[SJRiegel]

This would be a good time to use Text Variables.  

Each of the second and third boxes would pull the text content from box 1, with whatever new formating you applied to it. 

[TᴀW]

Use linked content.

Select the text that you want to have appear in various places. Or the entire text frame if you prefer.

Then: Edit > Place and Link

This will load the placegun with the text content and you can click anywhere in the document to create a linked copy of the text inside its own text frame.

Now when you change the original text, you will see a little yellow triangle next to the copy to show that it is linked and out of date. You will see a similar triangle in the links panel.

Clicking on the yellow triangle will update the frame to match the modified original.

There's much more to this feature than that (https://helpx.adobe.com/ca/indesign/using/linked-content.html), but this is a good start.

Ariel