To correct the grammar and eliminate unnecessary words, the instructions could be revised as follows: Create a presentation and when you reach the last slide, if you have additional information to include, integrate it into existing slides. Alternatively, add a new slide: Click on "New Slide" in the Task Pane or select "New Slide" from the "Format" menu.

To improve the grammar and conciseness of the instructions, you could rephrase them like this:

"Create your presentation. If you need to add more information after the last slide, incorporate it into existing slides where appropriate. If necessary, insert a new slide by clicking 'New Slide' in the Task Pane or by selecting 'New Slide' from the 'Format' menu."

Extra: When giving instructions, clarity and brevity are crucial. The goal is to convey steps in a manner that's easy to understand and execute, without any extraneous details that could confuse the audience. In this context, a presentation refers to a series of slides created using software like Microsoft PowerPoint or Google Slides. These programs typically have a Task Pane where you can perform various actions, such as adding new slides. Additionally, the menus at the top of the screen, such as the "Format" menu, contain options for adjusting the presentation's appearance, including adding slides. When integrating additional information into a presentation, it's important to keep the content relevant and organized, enhancing the presentation without overwhelming the audience with too much information on one slide.