If the pics are in the same folder and they are next to each other - left click on the first one then hold down shift and left click on the last one. Those 2 pics plus everything in between will be selected. Press the delete button on your keyboard.
If you want to add individual pics to the selection hold down Ctrl and left click on the pic, to remove a selected pic hold down Ctrl and left click on it.
You can also hold down the left mouse button and drag over the pics you wish to select.
To select all pics in a folder use Ctrl A