Question

To insert text from a separate file into your word document,

Answer 1

To insert a separate text, I believe you need to highlight, copy, and paste. You need to copy the separate text and paste it into your word document. (Don't forget to cite the source, if it is not your own).

Answer 2

I'm not sure if this is the answer, and if it isn't, please delete my comment, but I think the answer would be to highlight the text and to copy and paste.