Tell me how you assign the keyboard characters or function keys to Autocad commands?

1. Run CUI.
2. On the left pane, expand ACAD > Keyboard Shortcuts > Shortcut Keys.
3. Click Toggle Ortho.
4. On the right pane, go to Properties > Access > Key(s).
5. Click ...
6. Enter F4 to assign it.

If you want to assign the function key to other commands, drag the command from Command List to Shortcut Keys. Then repeat the steps above