Right click on the newly added map layer.
Click "Properties…"

Right click on the newly added map layer.

Click the "Transparency" tab. \
Change the transparency to about 80% and click "OK".

You can also click the check mark on the map layer to turn it on/off.

You final map should look like this!

Now is a great time to save your project (Ctrl/Cmd + S).

With some transparency, you can begin to notice differences between the two maps and how Tuscaloosa has changed over time.

QGIS Georeferencing Tutorial 10: Adjust Transparency and Save