Use the WidgetComponent in your blueprint to place it in the world
To make it look like when you type that there is suggested text, I suggest you layer two Text Boxes over each other, the one in front to have them type in, the one in back, to have the same starting text plus the next suggested word appended at the end. Also make the text in back a different color, like a lighter gray. Whenever the text in the typing box updates, update the backing text.
The algorithms for text prediction / interpretation are up to you.