Can someone explain this to me??

ok so line the pics up in your folder tht u want to アップロード side によって side, Then, hit the "ctrl"button and at the same time click on ur 1st pic then keep clicking while pressing ctrl, it should look like this so there should be frames around the pics u selected. hope this helps !

When あなた choose the 画像 あなた must press the shift button to select many 写真 at the same time
Try it, It works with me :)