In Autocad, How do I assign keyboard characters or function keys to AutoCAD commands?

Go to Manage Tab---- user interface------keyboard shortcuts---- temporary override keys 

Endorsing answers given by fellow experts

You can create multiple paragraphs of text together in a multiline text object (textmult). With your built-in editor, you can format the text appearance, columns and outlines.After specifying the point of the opposite corner when the ribbon is active, the ribbon contextual tab Text Editor is displayed. If the ribbon is not active, the In-Place Text Editor appears.If you specify one or the other option, or if you enter -TEXTMULT on the command line, TEXTMULT does not use the text editor on site and displays additional prompts.