Open Google Photos on your device or go to photos.google.com
Select the photos you want to transfer
Download the selected photos to your device
Open iCloud Photos on your iPhone, iPad, Mac, or go to icloud.com/photos
Make sure iCloud Photos is turned on in your Apple device settings
Upload the downloaded photos to iCloud Photos
On iPhone or iPad, use the Photos app and import or add the downloaded images
On Mac, drag the downloaded photos into the Photos app with iCloud Photos enabled
On Windows, install iCloud for Windows, turn on iCloud Photos, then upload the photos through the iCloud Photos folder
On iCloud.com, click the upload button and select the downloaded photos
Wait for the upload to finish and confirm the photos appear in iCloud Photos