There are a few different ways that you can create a route on the Google Earth app.
One way is to use the "Create a Layer" button, which can be found in the "Layers" menu. Once you click on this button, you will be prompted to name your layer and choose a color for it. Then, you can use the "draw a line" tool to draw your route.
Another way is to use the "Places" menu. In this menu, you can use the "add a place" tool to create points along your route. Once you have added all of the points, you can click on the "Create a Route" button. This will allow you to name your route and choose a color for it.
You can also create a route by importing a GPX or KML file. To do this, go to the "File" menu and choose "Import." Then, select the file that you want to import and click "Open."