Creating a presentation can be just as simple or complicated as you would like it to be.
Using a tablet such as iPad, the simplest possible way to do it is just to use your photography application to photograph your slides and put them in an album in the proper order.
The album can then be projected from your tablet, or even smartphone.
You could create text slides by making them in a word processor and printing them out and then photographing them from smartphone or tablet.
These printouts could also be more precisely scanned such as with Google's Photoscan or from iPad by using iPad Notes scanning. Both can frame the slide and square It off. Seems a bit complicated but once you get used to it, it's Duck Soup.
That might be an easy way to get started if you're just getting into it.
The next more demanding step would be to use a Presentations application. The Microsoft Powerpoint presentations app was one of the first. Later on came Google Docs and Keynote for Apple products including iPad. Powerpoint came with a thick book.
These dedicated applications enable you to enter text slides and then all the other fripperies such as transitions.
Such applications typically show your slides as thumbnails to the left of the screen from top to bottom with the current working slide in the large window at the right. Rearranging is done with drag and drop. The same apps run the slideshow, once created.
Creating text slides in any of these dedicated presentations applications take some getting used to.
Your first create a new slide in the presentation software app.
Typically you then double click to get into an editing mode window where you can control the slide and the formatting, including typeface and type size.
The editing window is usually surrounded by a dotted frame.
The text window frame can be moved and resized.
Where touch screens are available this can be done by touch. It’s tricky, touchscreen or not.
I have usually used Google Docs for its simplicity.