How do I create a photo collage WITHOUT using presets and autofil?

@Armen16B8 said:

Except that when I open a picture, I can't copy it unless I draw a rectangle around it. Then I can copy and paste as a new layer in the blank document.

Try the following, illustrated in my screenshot:

• Once you have created your new document (1), make sure that the Photo Bin is toggled on (2). 
• All of your open photos will now be displayed in the bin (3)
• You can now click and drag any photo to the new collage document (4).  This will create a smart layer (which may cover the entire document).
• You can resize and position the photo using the handles that are present at the corners (5).  Once you resize and position the image, make sure you click the green checkmark confirm button. 
• To resize or reposition an image, select the layer and press Ctrl+T to transform that layer again.

I don't know how PSE15 works (also using old version), but I should hope you can still do these very basic steps:

1. Create a blank canvas to place your pictures.

2. Open a picture and select it: Select > All.

3, Copy the picture to the clipboard: Edit > Copy.

4. Activate the blank canvas and paste from the clipboard: Edit > Paste. This places the picture on a new layer with transparent background.

Repeats steps 2-4 for the other pictures.

Now you can resize, re-position, and rotate the pictures, crop them to whatever shape you like, add effects such as borders, frames, drop shadows, and add text inside or outside the pictures.

To overlap the pictures, rearrange them in the Layers Palette.

Here I added a blue background and created frames using the Wow Neon Layer Style.