Open your Google Slides presentation and navigate to the slide where you want to draw.

Click on "Insert" in the top menu bar and select "Line" or "Scribble" from the dropdown.

Use your mouse or trackpad to draw freehand on the slide.

To adjust the drawing, select it and use the toolbar options to change color, thickness, or style.

If you need shapes, go to "Insert" > "Shape" and choose from available options.

Move or resize your drawing as needed by clicking and dragging the edges.

Once satisfied, save your changes and review your slide.