Photoshop :: Put In Massive Pictures Into A Picture?

I'm making animation so what i was do was to convert a video i made to picture to later put into PhotoShop and make animation there (i know i can convert to gif, but i like more to edit the animation too etc).

Here im gonna try explain what i need help with:

I making a new picture (or what its named, pressing file and new).

I make it 720x480 because that is all my pictures i need put into this picture i make.

When i got this white 720x480 i want to put in like 100 pictures that all is sized 720x480!

Here the problem comes.. When i put in the pictures its not coming into the white one! Its comes new

I want them come in, i've also tried make a marquee around the white (also pressing ctrl + a).

But not working!

So what i need to do is to go to a picture and press ctrl + a and ctrl + c and go to the white one i created and press ctrl + v

and then go to the next, and so on!

This takes time and i guess it would work to put in pictures directly so it will be layers in the white picture i was create in start.