Select the text with the type tool
Edit>Paste in place
or use the shortcut as described in the Edit Menu
Maybe I wasn't clear. I want the text, not box, to be incorporated into an already made template style. In effect, I want to retain all the GREP styles in Heading1 and merge the style with the font, size, colour of the text I select.
You're still not entirely clear, Are you saying you want to redfine the style to use the font specs from the unstyled text while retaining other attributes, like GREP and Nested Styles?
If that's the case, redfine the styles first to use the parameters you want, then use Find/Change to find the text that has the parameters you want to assign that style to.