To upload a multi-plant photo, look to the left-hand edge, blue "menu bar".
Click the ninth item down, "Goodies".
On this screen: "All Things Plants Apps", click on the fourth item:
"Multi-Plant Photos - Share photos of your garden and name each plant shown."
The next screen is: "Multi-Plant Images"
Click on "Add a Multi-Plant Image"
Click on "Click to Upload an Image".
Browse to the folder on your PC that you want to upload a multi-plant photo from.
Then I think it gets trickier since you have to draw rectangles and enter names of plants somehow.