To select multiple files click on the first file, and then press and hold the Shift key. While holding Shift, click on the last file. This will select all files between the two options
How to select multiple files that are not grouped together: Click on the first file, and then press and hold the Ctrl key. While holding down the Ctrl key, click on each of the other files you want to select.
You can also simply select multiple pictures by selecting them with your mouse cursor.
To begin the selection of images you will first need to start creating an album by following the instructions located here: How to start an album project
Once in the album editor click on this button and than on upload
Clicking on upload will open the folder menu of your computer. From this point on just follow the instructions in the beginning of this article