Go to the "Start" menu, then go to "Programs," then open "Windows Movie Maker."
Click on the "File" drop-down menu, then click on "Open" to open an existing video project. Select your project from the "Open" window, then click on the "Open" button.
Go to "Tools," then click on "Credits," and then click on "Titles and Credits" from the drop-down menu.
Choose the "Add title on the selected clip in the timeline" option.
Click on the iMovie icon in your dock and wait for it open. Then click on "File," then "Open" to open your existing video project.
Go to the "Edit" menu, then click on "Split Video Clip at Playhead." Click on "Editing," then "Titles." Then scroll down the list until you see the "Subtitles" option, then select it. Select the size, color and type of font for your subtitles in the "Options" menu below.
Select the first segment of your movie that you want to add subtitles to, then type the desired text in the right window, and then click on the "Add" button. You will have to repeat this process for each segment you add subtitles to.