Open a window showing the contents of the source folder where the photos are stored. (You need the window to take up about half of your screen. If necessary, click the 'Restore down' pair of overlapping squares in the top right-hand corner and/or drag the edges of the window to get a decent fit).
Now open a second window showing the contents (or lack of them) of the destination folder, where you want to copy the images to. Make it about the same size as the first folder, so that the two folders are positioned alongside each other.
To copy a SINGLE photo from one folder to the other, simply 'drag and drop it', using your mouse.
To copy ALL of the photos from the first folder to the second one, click in the first folder (to ensure that it's the 'active' one) and hit Ctrl A to highlight all of the images. Then drag & drop the lot together.
To copy a BLOCK of photos across, click on the first one in the block, then hold Shift down as you click on the last one. That will highlight the relevant block, which you can then drag & drop.
To copy a SET of individual photos, click on the first one, then hold Ctrl down as you click on each of the others that you want to select. Then drag and drop the set across to the other folder.