Add company logo to top left of screen

Question

I would like to add my company logo to the top left of all screens, replacing the Salesforce logo:

How do I do this in the Professional Edition? We have already created the custom app with our logo.

Thank you!

Deepak K Anand · Accepted Answer

Well then you should then change the selected App to your Custom App via the  App Menu  =

Erika Liljefelt · Answer

Apologies, we created a home page component, not the custom app. Now I've created the custom app and it works! Thanks!

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