How to create a multiple image on photoshop

1. On photoshop open up the image that is going to be your background image. Then open up another image which you are going to put over the background image.
2. Go to layer, then layer mask and click reveal all so that you are able to rub in or out your image into the other.
3. To rub in or out an image you need to make sure that the two squares at the bottom of the tool bar on the left are completely black and white. If they are not black and white when you use the brush tool it wont rub the image it will draw a coloured line onto your image. What these squares do are that they switch from the image below the image you can see and to the image you can see so that you can rub in the image from under the image you can see or rub out the image you can see so that some of the image below is shown.
4. To add another image ontop you need to open up the image you want to add and then repeat step 2.
5. Once you have done your multiple image you need to go to layer and at the bottom of the list click "flatten image". This will flatten your image so that it is just one layer.