Mood board on Adobe Photoshop...
All I do is make a big canvas...
File > New > and make a size maybe 8.5 x 11 inches (you can always change the size as you go)
Then I load in all the pictures I want to use...
I can even open, say, My Documents and drag images into Adobe Photoshop and they'll open there instantly
Then I pick a file... hold CTRL and press A (to select the whole image)
choose CUT from Edit
then go to the new file, the 8.5 x 11 white canvas... choose Paste from Edit
(When you press paste, you will see that it creates a New Layer... it will pop up in the Layers window)
To resize an image in your board
Click the layer of the image
Choose the arrow icon in the toolbox (located at the top of the toolbox)
Then underneath the buttons File, Edit, etc. ... You will see
"Show Bounding Box" --click that
--A box will appear around the image. Touch one of the square corners --your mouse will turn into an arrow with two heads-- and then under File, Edit, etc. you will see appear W: H: ...and so on. That will change the size of your image
--------------------------
You can also just use the arrow and move it about as you like, but if you use the W: H: using percentages, you won't skew any details of the original image
& for maybe more complicated questions, we have this thread
Questions for Adobe Photoshop