There are 3 ways for you.

1. Click Text > Logo Overlays. Here, select a favorite sample, and add it to the canvas. Then back to Media, drag the image you like to the logo frame.

2. Click the Replace button and select an image to replace the original logo.

3. Click to add a layer to the canvas.

You can change the logo's shape as well (remember to ungroup first if the logo sample you added has text).