well compress in your images in your Image Editor as you see fit...
but to use an image dynamically, is more or less like calling an image in HTML...(you link to it)...and the image in a directory within your website directory.
heres an example:
1.) make a blank/empty movieClip and drag it to our stage. (give it an instance name of containerClip)
2.) make a button
3.) put this code on the button:
code:
on(press){
containerClip.loadMovie("image1.jpg");
}
thats it! now to explain what you just did.
1.) First you basically created a "TARGET" to load your image into (this was the blank movieClip with the INSTANCE name of containerClip)
2.) you created a button that had the actions to LOAD our image into the containerClip. pathed to it: containerClip.
the you added the action: loadMovie();
and in the parameters you filled in WHAT you want loaded into the containerClip: "image1.jpg"
you can also create blank/empty movieClips on the fly (meaing you dont need to have a target already on the stage..you create one same tie you load the image
code:
on(press){
this.createEmptyMovieClip("containerClip", this.getNextHighestDepth()); // you can assign a level here instead of nextHighestDepth.
containerClip.loadMovie("image1.jpg");
}