Models and icons

I have dl the beta model pack from the dl section, unrar it.

I copied the folders to my War3 folder

With the world editor, I enter the path and everything works fine, the icons and models show up in the world editor as they are supposed to, but in the game, nothing shows up(Models are just a shadow for unit, and nothing for spells, icons become green.)

It sounds like you haven't yet imported the files into your map using the Import Editor.

While the files will show up in WE if you have them in the right place, they won't get added to your map until you manually add them. Get to the Import Editor by clicking the button that looks like a white page with a green arrow on the top of any window.

Once the files are imported, you're going to want to change the path (by double-clicking on the file in the Import Editor and manually re-entering it) to match the original path of the model or skin.

Keep in mind that most of the things from either of the beta packs will add a substantial amount to your map size, which is undesireable.