Then you probably want to use the Speaker's notes or Control Toolbox's
Textbox. During slide show, Right click and select Screen > Speaker's Notes.
This will bring up the speaker's notes where you can type your text from
there.

Another way is to use the Control Toolbox's Textbox.
Click View > Toolbars > Control Toolbox.
On the control toolbox toolbar, select the Textbox icon and place a textbox
on the slide. Now, go into slide show and you will be able to enter text on
the textbox.

You can use the Meeting Notes feature, but it will add a slide at the end of
the presentation, not on the slide itself...
In Slide Show view, right-click and select Meeting Minder; on the Meeting
Minutes tab, in the Description text box, type your notes;

You can also add action items if you'd like.  Add the assigned to and due
date, and click Add.  Click OK.

Hope this helps...