Using my computer, how can I duplicate a paragraph three times on the same paper?

In Word, copy and paste three times.

Without knowing what program you are using its hard to answer. But in most cases, you just select the paragraph, copy then paste as many times as needed.

Assuming you are really new to copy and paste here is a more detailed description of what to do. Using the cursor to swipe across the paragraph from beginning to end thereby highlighting it, you can then right click it selecting copy (or keyboard CTRL - C). This puts a copy of the text into your Clip Board. Then position the cursor on the page where you want the copied paragraph to begin using Left Click to place the cursor (or the Arrow Keys on the keyboard) and Right Click selecting paste (or CTRL - V with the keyboard). You can do this as many times as you want since the paragraph will remain in the clipboard until deleted, replaced with a new copy or you shutdown.