To change the default spacing between lines of text in PowerPoint, please follow these steps:

1. Open PowerPoint and select the presentation you wish to edit.
2. Highlight the text that you wish to change the spacing for.
3. Click the menu line that says Home.
4. Find the paragraph section of the Home tab.
5. Click the dropdown list that says Line Spacing.
6. Select the desired spacing for your text from the dropdown list.