Hi @LovePowerApps19
You can achieve this by following the below steps
In Portal Studio
1. Click on the header
2. Click source code editor at the bottom
3. This will show you a header web template
4. Add the following code to add an image on top of the home navigation
<img src="./ElevateWISEbanner.png" alt="ew" width="900" height="250">
Output:

The above is one of the simple ways. If you want an image exactly above the home text then you can play around with the web template. The idea here is to add the <UL> tag and add the image as above then you need to play around with a little bit of CSS to align it above the Home link.
Hope it helps.
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