The "My Places" tool, found on the left-hand panel gives you the ability to create a library of tours of your own making or by saving others. You can also import KML files into Google Earth making it easy to bring in those KML tours you created in the old Google Earth.
Start by clicking on the "My Places" tool on the left-hand panel. A sub-panel will open showing you all of the current tours you have saved as well as any places you have bookmarked. The ext section will focus on bringing in new KML files. Notice you can turn files on and off by clicking on the "eye" icon to the right of the files. You can also delete a file by clicking on it to select it and then clicking on the trash icon located at the top of the "My Places" panel.
You may have some older KML files on your computer or have run across them on the internet or you may want to explore a specific topic and have begun the search. This section will look at how we can bring in KML files from other sources. The most difficult aspect of this process at times is finding the KML files. The best thing to do first is begin by searching for specific data sets. When you search for KML files make sure you include KML in your search. For example, if you are searching for recent US earthquake data, your search may be, recent us earthquakes kml. Once you have located a KML file you can download it to your local computer or to Google Drive.
To import the file into Google Earth, click on "Import KML File" located at the top of the "My Places" panel. Navigate to the folder where the file is located and then click on open. A new sub-panel will open where you will be able to see the KML file on Google Earth. Notice you have the ability to save the KML file to "My Places" or you can discard the file. In some instances there are several folders that make up a KML. You have the ability to turn off individual folders within a KML file. Depending on the type of KML file, some will update automatically, as is the case with the earthquake KML from the USGS.
You will also notice a couple additional icons at the top of the "My Places" panel. The tag allows you to rename a KML file. The "Zipper" let's you make a KMZ file (a zipped version of a KML). And the three dots give you the ability to duplicate a KML file and export a KML file.
There are additional places to find KML files. You can import KML files from Google My Maps and Google Tour Builder.